This mod contains:
1.Weapon Rebalance - since vanila Battletech game is to easy (I have completed my first run withou using any of Assault mechs., even then my mechs hardly any time took any structure damage!), some weapons are completly OP like LRM's and other mostly Long Range weapons are ussles i have rebalenced them but not by decreasing damage of weapons like other mods do because that results in decresing game dificulty (Mech controled by AI have fixed number of weapons so if you  decrese damage of MediumLasers its Weight or HeatCost you make enemy mechs weaker and players mechs stronger, which makes game even easier than it is currently.

So in this mod I have inresesed damage of underpowered weapons to make them useful (this also increases game dificulty because it increases damage output of AI mechs), also now all weapons are fairy balanced in terms of their damage output but they have its unique futures. Laser weapons have highest damage output and bonus to accuracy but they don't do stablity damage for high heat cost, Missiles do moderate damage and stability damage with moderate cost in weight and heat, AutoCanons have lowest damage output by highets stability damage, also they inflict highest damage per shot which can destroy Mech components in 1 voley, they cost the most in terms of weight but have lowest heat generation.

Since combat in this game is turn based and damage output of mechs is related to mass of the weapon, ammo mass and heat generated by weapon, I have created formula to calculate EfectiveDamege=ED of weapons to easly compare them.

This formula look like that:
ED= (weapon damage) / ((weapon weight) + (ammo for 10 shots weight) + (heat generated/6))

In vanila damage output of weapons is just broken some are OP like hell and other are UP
So lets compare wepons using ED:

ED-VBWW- Efective Damage of Vanila Basic Weapon Wariant
ED-VHDW- Efective Damage of Vanila Highest Damage Wariant
ED-MBWW- Efective Damage of Moded Basic Weapon Wariant
ED-MHDW- Efective Damage of Moded Highest Damage Wariant
              ED-VBWW      ED-VHDW       ED-MBWW      ED-MHDW
LRM5        5,88               8,82                 4,82                6,15
LRM10      5,13               7,69                 4,82                6,15
LRM15      5,61               7,41                 4,82                6,15
LRM20      5,48               8,22                 4,82                6,15

In vanila LRM's are just broken they have highest ED of all long range weapons, thye do insane stab. dmg and on top of that thye can use indirect fire with -3 accuracy which can be reducet to 0 by training pilots. So in mod I had to nerf LRM's. I have reduced their stab. dmg. by 50% basic wariants do 1 stab. dmg. per missile fully upgraded wariants do 2 stab. dmg., I have removed +2dmg and +2stab. dmg wariants of LRM's, but I have added +1dmg +1stab. dmg. variant to the game, I have alos slightly cheanged weight and heat generated by LRM's. Even after all those cheanges LRM's still have the highest ED of all very long range weapons
and still can use indirect fire, so I have increased indirect fire penalty from -3 to -6, and now finally LRM's aren't OP anymore, and you can try to use something else for long range ;)
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                  ED-VBWW      ED-VHDW       ED-MBWW      ED-MHDW
MLaser        9,35                13,1                 9,35                 13,1
SRM2          7,27                 10,9                 7,27                 10,9
SRM4          8,57                12,86               7,27                  10,9
SRM6          8,09                12,3                 7,27                  10,9
Ac/20          4,96                5,96                 6,21                   7,76

As you can see in vanila SMR's4, SRM's6 and Ac/20 are creally unbalaced since fully upgraded variant of SRM's also inflicts 5 Stability Damage per missile which made them the best weapon for medium range. I have modified SMR's and Ac/20 so now SRM's are no longer OP, they offer moderate damage and moderate stability damage since I have reduced their base stability damage from 3 to 2, and i have removed +2 Stab variants. Now SRM's can do max 3 stab, dmg per missile. I have increased base damage of Ac/20 to 120 DMG (Upgraded 150DMG), and i have reducet the heat from 25 to 20 but still Ac/20 has the lowest ED of medium range weapons, but it does highest Stab. Damage and have highest chance of destroying mech part in 1 shot. Now Ac/20 maybe will be worth using.
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              ED-VBWW      ED-VHDW       ED-MBWW      ED-MHDW
LLaser     4                     5                      5                       7
Ac/10      3,8                  4,4                   4,76                  5,71

The long range weapons in vanila were fairy balanced betwen each other but thye are greatly undepowered in compareson with medium range weapons especialy fully upgraded wariants had almos 1/3 ED of MLasers which made LongRange weapons ussles. I have incresed damage of LLasers and Ac/10 so now they have about 1/2 ED of medium range weapons, which makes them useful for a cheange. Also I have increase long range fire penalty from -4 to -6 for all weapons so now there will be more reasons to actualy use long range weapons.
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              ED-VBWW      ED-VHDW       ED-MBWW      ED-MHDW
Ac/5       4,3                   5,3                   4,78                 5,73
PPC        3,66                 4,3                   4,39                 5,49
Ac/2       3,46                 4,84                 4,15                 5,53

From very long and extreme range weapons Ac/5 was creally the best it was even better than Long range weapons in terms of ED so in vanila there was no reason to use anything else than Ac/5. In mod Ac/5 has slightly higher ED than Ac/10 but it does much less stab. damage, PPC now inflicts -2Acc debuf on to enemy mechs with good damage, and stab. damage but building heat eficient dual PPC mech still isn't easy, and its real ED will be much smaller than Ac/5 mech. ED of Ac/2 my seam to be a little to high but its hard to find a good mech that can use at least 4 of them to actualy make them usseful, I have never used them in vanila so I'm hoping that now there will be reason to use them. 
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               ED-VBWW      ED-VHDW       ED-MBWW      ED-MHDW
Flamer      5                    10                    5                       10
SLaser    15                    22,5                 15                     22,5
MG          21,4                 21,4                 21,4                  21,4

Short range weapons have remain the same. Flamers still suck but now it is easier to find +5dmg flamers in the stores and this variant is almost worth using in compareson with other weapons. Machine Guns Have the best ED but there are no upgraded variants of them in the game so fully upgraded SLaser variants are actutualy sligtly better than MG, also its worth mentioning that shord range weapons ignore enemy evesion bars, so you can get close to the enemy that has high evasion amd shoot him into oblivion with suport weapons.
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                                                         ED-VBWW     ED-MBWW
Extended Range Small Laser          6,6                  10
Small Pulse Laser                             9,38               11,25
Extended Range Medium Laser     4,84                  7,14
Medium Pulse Laser                        6,92                 8,57
Extended Range Large Laser          3,2                   4,6
Large Pulse Laser                             3,3                  4,7
Extended Range PPC                       3,26                4,57
Gaus                                                  4,39                5,27 

Forgoten tech in vanila is bassicly useles piece of junk, I this mod I have cheanged their ED so now forgoten tech can compeat with basic variants of standard weapons because thye offer some bonuses over them like longer range, higher accuracy, or higher damage per shot, ERPPC has greate ecective range and DMG but doesn't inflict -2Acc debuf, but forgoten tech loses to fully upgraded wariants of standart weapons (thats why its not used any more), hoever now it may be possible to play the game using only forgoten tech. Now forgoten tech can be bought in stores but it isn't cheap.

Other weapon cheanges:
I have fixed some weapons bugs from files when some wariants of missiles had +5 Acc., to much stability dmg. and so on (I have no idea how devolopers haven't fixed such obwious bugs before release...)
2. This mod alos includes Lost tech mod which ads Lost tech to the stores, weapons and double heat sinks (which i never use becaus it would make game to easy - hoever if you would like to play only with Lost tech mechs 
then using Dual Heat Sinks shoulden't be OP) - any way Lost tech is rather expensive.
3. It is now easier to find mechs in store (if any one likes to buy them for those absurdly high prices)
4. Combat speed has been increased, all units move now with 2x speed and downtime betwen turns have been reduced.
5. You can now skip 2 or even 3 tuturial missions if you want.
6. I have modified Evasive Movement so now it ads 2 evasive charges on move, but max number of evasiv bars havent beed cheanged, this makes Evasive Movement Perk slightly less useless, but to fix Perk system it would be necesery to cheange Bulwark so it would give 25% cover not 50% as it is currently also i should stack with forest etc to for full 50%, but i have no idea how cheange those perks in the files - so for now we are stuck with shity OP Bulwark + Precision Shoot combo which makes game way to IMBA.
7. I have lowered rarity of all Lost tech weapons from 20 to 4, and i have cheanged rarity of other weapons, those that had rarity 0 or 1 remain unchanged, rarity 2 has beed cheanged to 1, rarity 3 cheanged to 2, rarity 4 cheanged to 3, rarity 5 cheanged to 4, hopefully it will make those weapons easier available in the stores. Rarity of other items like ammo or gyros haven't beed cheanged.
8. I have few hours of gameplay with this mod, and everything seams to be working fine (I have even lost few mech components in battles, so its slightly harder than vanila), maybe except PPC, i'm not sure if its aplaing debuf correctly, but i know for sure that debuff stacks so it kinda work as intendet.
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Mod Files and Installation:
For weapon rebalance mod copy files from weapon folder to C:\Program Files (x86)\Steam\steamapps\common\BATTLETECH\BattleTech_Data\StreamingAssets\data\weapon
And constants\CombatGameConstants.json to C:\ProgramFiles(x86)\Steam\steamapps\common\BATTLETECH\BattleTech_Data\StreamingAssets\data\constants
It also fixes some incorect weapon values from vanila

If you want increase combat speed copy files from movement folder to C:\ProgramFiles(x86)\Steam\steamapps\common\BATTLETECH\BattleTech_Data\StreamingAssets\data\movement
And AudioConstants.json file from constants folder to C:\ProgramFiles(x86)\Steam\steamapps\common\BATTLETECH\BattleTech_Data\StreamingAssets\data\constants

If you want ad more mechs and lost tech to stores copy files from shops folder to C:\ProgramFiles(x86)\Steam\steamapps\common\BATTLETECH\BattleTech_Data\StreamingAssets\data\movement

If you want modifi Evasive Movement Perk copy file from abilities folder to C:\ProgramFiles(x86)\Steam\steamapps\common\BATTLETECH\BattleTech_Data\StreamingAssets\data\abilities

If you want skip 3 tutorial missions copy files from milestones folder to C:\ProgramFiles(x86)\Steam\steamapps\common\BATTLETECH\BattleTech_Data\StreamingAssets\data\milestones

If you want to install entire mod just copy and replace all file from data folder to C:\ProgramFiles(x86)\Steam\steamapps\common\BATTLETECH\BattleTech_Data\StreamingAssets\data\

If you want to tell me that my english is bad, then fuck of ! - learn mine if you are so smart, and make your own mod.

Enjoy.