I was playing around with the console to look for anything related to rarity of weapons and armor. Lo' and behold, the string "quality" got me there. I used 'help "quality" 0'. They seem to be in the category of OMOD.

I took note of them and tested which ones worked. UNFORTUNATELY, it doesn't work on armors(then again, I didn't test them extensively... you guys can, might be armor specific??). It works only for weapons, highest 'quality' I could get from weapons seems to be 'advanced', BUT, they seem to be stackable(I got my Equinox to do over 200 damage per shot). I think they are percentage damage increases.

Installation:
Just as you would any bat file, put the txt file in your GAME Starfield folder.

Usage:
Drop a weapon to want to mod on the floor.
Open console in game.
Click on weapon, use scroll wheel until you see 'WEAP' something on the screen if you don't see it.
Type in the console:

bat quality

Change damage instructions?
Just take away some of the lines in the bat file, I'm not going to sort them and figure out each one's percentage damage increase.

Requests then?
NO, I WILL NOT TAKE REQUESTS regarding specific issues with this mod. This is just a good starting point for someone else to figure out quality/rarity of items in the game. I just went for maximum damage I could achieve using my findings you guys can figure out the damage you want by modifying the bat file.

How about useful Notes??
I'll provide notes at least in a folder. It's the string names for each mod. There's also 'Quality Tiers Any' strings that I have no idea what it does, so I only used the 'Quality Level 01' to 'Quality Level 04' strings in the bat file. I've roughly noted them as 'tiers any' or '01'-'04' in the notes txt file. The ones in the bat file were the ones to seem to do anything, the others didn't change any of the stats.
There were 2 tiers that added both physical and energy damage:
1bdc47 added phys25 ene 22
and also
28f44b added phys25 ene 22

THE REST IS UP TO THE COMMUNITY. GOOD LUCK.