After playing through BG/ToB who-knows-how-many times, there remains one gripe that just annoys me: BG2's items, particularly weapons.
Don't get me wrong, there is a large number of them and fairly nicely spread out; but what gets me is how weirdly they are organized.
The main problem is weapon types. Ever tried finding a bastard sword worth using? There's literally TWO unique bastard swords in the entire game (Jhor the Bleeder and Foebane)! And this is bastard swords, not some exotic weapon you wouldn't see every day in this part of the world.
How about Maces? A single +3 mace in BG2, a single +5 in ToB - again only two weapons worth using in an entire category. Warhammers? Clubs?
Some categories of course are better designed (Long Swords, for example), while others have at least a reason to be rare (Katanas).
I think one reason for the large amount of "useless" weapons is the power creep in BG2. A +1 weapon is already bad, a +2 is borderline acceptable for BG2, and by the time you get to ToB you can't even hit a lot of enemies unless you have +4 or better.
One mod that tries to address this is the ItemUpgrade mod. While the concept is great and very fun to do within the game, the resulting weapons are often unbalanced; and in any case, they are balanced around existing weapons, meaning they can't really remedy the scarcity of certain types.
What I propose now is an almost complete redo of BG2/ToB's weapons. Take those +1 sticks-with-a-story and make them worth using! But make no mistake: I'm not saying you should make all weapons +3 and add Dread Mauls of Doom to every goblin's loot table - in fact, part of the mod should make sure to distribute the weapon's within the world in a way that makes for a more linear power curve.
There's two parts to this: availability by story chapter, and availability by party power. An example of the first would be Bernard in the Copper Coronet selling stuff only after the slaver quest is done, or Ribald selling items only after the Underdark; an example of the second would be Firkraag holding Carsomyr.
Care would have to be taken to balance around this VERY carefully. Daystar, for example, should no longer be accessible to anyone able to pick the lock on the chest and run - the Lich guarding it would have to be actually defeated. Items added by the mod could be distributed in similar ways, possibly even with a system of randomization that shuffles powerful items around the loot tables of powerful enemies.
As for story-gated items, there should be more distinctions than just before/after Underdark. Completing some of the major side quest lines, for example (Cult of the Eyeless, Umar Hills, etc.) could unlock items in certain locations. These could either be for sale, or clevery hidden (above mentioned randomization comes into play again?).
Also, the items should roughly be distributed in a way that has a more smooth flow of upgrades: things could start of with +1 mainly, and a rare +2 or two, as you make your way through Athkatla. Doing side-quests would see more +2s, with maybe a +3 or two at the end of major lines (not as a reward, but an unlock, see above). During the Underdark, +3 would become more common, and afterwards +4 or the rare +5 (really rare, like Carsomyr) could be earned through major challenges.
A tie-in that would support this very well would be an expanded upgrade-system. Cromwell's some-assembly-required-style artifacts are pretty cool - they could do with a little more beef, though! When was the last time you used The Wave? In addition to these fractured gems, upgrading of existing items through unusual and rare components would make sure that you have something to work with for the rest of the game. I'm not talking about making everything +5 - but if, say, you got a unique Mace+1 (Ardulia's Fall, for example) early in the game, you could make it a +3 or even +4 at endgame by acquiring certain materials. It would be great to introduce some choice there: limited availability of components, but multiple possible upgrades (think Eye of Tyr). There could even be multi-tiered upgrades (say, +1 -> +2 at first, and then +2 -> +4 at endgame, on the same base item).
It would be important not to overdo this, of course. It shouldn't devolve into a farm-fest, and some of the more powerful items found naturally should remain 100% competitive (and un-upgradable). This is where the ItemUpgrade mod falls short, as it sometimes produces +5 monstrosities that blow everything else completely out of the water, including ToB items. Items should feel powerful, but not overpowered!
I've been talking a lot about weapons, but the entire concept could be expanded to other items as well. But the glaring imbalances of weapon distribution aren't as prevalent in other slots, and most of the BG2/ToB gear is actually quite well designed and distributed. There could be some improvements, to be sure, maybe a nice jewel or two to aim for. Mage robes in particular seem a bit lackluster; I'm not talking about Robe of Vecna 2.0, but say a Robe of the Archmage with an extra 4th level spell, or something along those lines. Small gifts, not powerhouses. Non-armor magical equipment especially (bracers/gloves, jewelry) should remain rare and special, not something you find under every rock. Upgrades could come into play here as well, maybe turning a +1 Ring of Protection into a +2 with certain components, or add some "special effects" (small THAC0 bonus, small spell bonus, small extra saving bonus vs. X, that sort of thing - small being the operative word).
The "big picture" should always be kept in mind: overall balance between equipment types/slots, power balance throughout the various stages of the game, and slow but consistent power upgrade. The last point in particular would be very important, I feel - nothing of the highest tier should be easy to acquire, no challenge should be "cheatable" (like, say, Daystar, i.e. run in, open box, run away).
I can't be the only who finds character creation unduly limited by weapon availability. I KNOW I'm not going to get a decent bastard sword until halfway through ToB - so why give my char that proficiency? I laugh every time I read the Katana proficiency description... "very rare" indeed, when you can get THE best Katana in BG2, and without ToB arguably THE best weapon in the game, with very little effort (in the unmodded game of course)!
There's tons of small details I can think of for such a mod, and I'd be happy to contribute. I've been playing BG2 for a decade now, and I've given many aspects some deeper and serious thoughts. What I can't do, however, is code all this - I am a complete klutz when it comes to techie-stuff, and that's putting it mildly. If there is anyone, any group, who would consider making such a mod (especially with BG2:EE in mind), I'd be very, VERY happy to make it a reality. BG2 is an amazing game, and amazing games deserve to have EVERY crease ironed out. We have the technology...!