Overview
I did not like vanilla Morrowind enchant mechanics, and I felt inspired today to make a mod for that; thus this mod changes the enchant mechanics to my liking.

• Enchanter's enchant skill and intelligence now affects the enchantment cost, allowing for stronger enchantments at higher skills. This feature is soft-capped to prevent exploits (formula below).
• Constant effects enchant costs are now scaled based on the soul size. With a God soul, you can now make true artifacts.
• This means that different NPC enchanters can make stronger or weaker enchants based on their skill.
• Additionnal enchantment effects do not anymore add previous effects costs.
• Min/Max sliders are tied for constant effect enchantments. Variable magnitude CE are no longer possible.
• Small QoL addition for spellmaking/enchanting : min/max sliders can now drag the each other.
  

Detailed description
- Enchanter's skill and intelligence effect -
Enchanter's enchant skill and intelligence now affects the enchantment cost, allowing for stronger enchantments at higher skills.
The cost is now divided by the following modifier : 
modifier = (0.666+(1.0-0.666+0.2/0.333) * (1-10^-(<enchant>*0.95+<intelligence>*0.05)*0.0033)))
modifier = min(modifier, (modifier-1) * 0.333 + 1.
Thus, an enchanter with 0 enchant and 0 intelligence will have its enchantment cost divided by 0.666 (thus, a maximum of 1.5 times more costly enchantments).
The divider quickly raises to 1.0 (Vanilla cost) at about 60 enchant/60 intelligence. Past the value of 1.0, the modifier change much slower and will asymptotically raise to 1.2.
Thus, a enchanter with maximum stats will roughly be able to make 5.4% stronger enchantment comparatively to vanilla. An enchanter that could get in a situation where he gets fortify 1000 intelligence and fortify 1000 enchant will be able to make items that are roughly 19.98% stronger than vanilla.
- Soul size effect on constant effects enchantments -
Constant effects enchant costs are now scaled based on the soul size. Using base soul charge of 400 as reference for constant effect enchantments, the enchantment cost is divided by the following modifier:
modifier = (<charge>/400)*0.5 + 0.5
Thus, Vivec's soul (1000 charge)  will give a modifier of 1.75 allowing 75% stronger enchantment compared to vanilla.
This feature can be combined to mods than reduces the soul size required for constant effects allowing the player to make weak constant effects enchantment at low levels. For example, with no lower limit, a mudcrab (charge = 5) will allow to enchant with roughly 50.6% capacity compared to vanilla.
- Additionnal enchantment effects do not anymore add previous effects costs -
In the original code, the cost of each effect is multiplied by number of effects that follows + 1. Now it is only multiplied by one, always.

Source
https://github.com/alex2603/openmw

Installation
I provided a portable installation of OpenMW 0.49.0 built with the modified source code. Unpack where you want and run like your normal OpenMW installation.

Issues
I haven't thoroughly tested the mod yet. I you find any issues, let me know.

Compatibility
Not compatible with a custom executable. Currently built for OpenMW 0.49.0 only. 

Suggested mods
Enchanting Enchanting - Improvements on Morrowind's Most Enchanting Skill
Oblivionized Constant Effect Soul Gems
Enchanting Made Possible

Future works
Provide configurable values / Balance work.
Figure out how to make this as a Lua mod / Propose modifications to the Lua handlers to make a mod like this possible.

Also, its my first and only mod, and I'm not that familiar with the modding community ... I'm not a programmer either so I'm not sure that was the right way to add this functionality. Anyways, feel free to share any feedback.

I might do a similar thing for alchemy or spellmaking in the future (soft capping effects potency and durations, preventing cheesing spells).