Old-time translator/modder here who would love to get his hands on some features for mechanical part of the game.
1. Adding an option for Stat: Weapon Proficiency opcode
Vanilla BG2 opcode for Stat: Weapon Proficiency worked a bit different than the one in BG:EE. Many modders (me, Demivrgvs from Revision mods) would still love to use it that way. The shortest explanation possible.
Old opcode was setting the proficiency on certain level as long as it was higher than current one which allowed us to for example use it to grant Fighters proficiency (+) in all weapons without touching proficiencies he already mastered (+++).
New opcode is additive only. So when we'd grant Fighter +1 bonus to proficiencies in all weapons which is not what we seek (as that'd allow Fighter to obtain Grand Mastery faster than intended). While additive proficiency modifier is cool for many people, we'd love to see an option to restore it to the old way.
2. Adding Kits to proficiency tables in terms of their starting/rate.
My idea was to give Fighters 2 free proficiencies at level 1.
But I don't want Wizard Slayer and Berserker to get that.
That'd help a lot.
3. Possibilities of adding alternative stats for Weapon Proficiencies/FIghting Styles
My idea to rework proficiencies would be removing the Attacks per round part of it (moving it into Classes - Fighter at level 7 can do 2 attacks per round, 3 attacks at level 13) while granting Attack Speed Factor bonus for being proficient.
- The possibility of changing the list of available Racial Enemies (it's using Race.IDS list, I'd rather swap it for something different, more general [Aberrations, Constructs, Humanoids, Monsters, Animals]
- Capability of increasing the bonuses from Racial Enemy (or new bonuses) based on Ranger's level.
- Capability of excluding Racial Enemy feature from certain Ranger kits.
Also, Externalizing Paladin's +2 bonus to all saving throws. It's disgusting.