Some mecanics exists and can be a part of the game without breaking inventory minimum management, immersion/reality feelings.
As you said, taking back arrows on bodies you just pierced, specific bags, finding arrows on ennemies dead archers or on their armory, someone talked about crafting...
There are a lot of possibilities that can be designed for this specific gameplay element to be a part of the game with the minimum risks to have to travel to a town during a long dungeon.
And this is also sometimes, I guess in less dangerous situation to force players to play a bit another way with his characters (ranged characters are probably less effective without ammo, but they are never useless).
Can't see the link with mana potion, breaking weapons and so on... Yes it's another way to improve realism but it's not what we're talking about.
Too much realism on every points is not always good I agree... But I really wait to hear someone saying it's a HANDICAP in BG1&2 (which is not the same as saying "I don't like it" or "I don't find this mecanic usefull").
