ToME WikiNerdanelVampire: This is a yet another potential solution to the dungeon litter problem.
At the moment objects can only ever be out-of-depth but never out-of-height. Because of this, going deeper down shallow items never become more scarce by any other means than out-crowding by deeper items. I think there isn't really much point in having all of those low items in the deep dungeon. Sure we can have some just to keep the game interesting, but I think we currently have far too much stuff that's effectively junk.
The idea of out of height is that when an item is attempted to generate much deeper than its effective level (from base item + additional qualities) it has to pass a die throw. Even though this throw is more permissive than the OOD throw, it still changes the distribution quite a bit. (Even as now, items like rations of food can have multiple depths defined.) The increased drop quality would make it necessary to mskr deep drops smaller, so that the piles would be no more.
This idea could also be applied to monsters. I think Steamband does something like this with monsters at least, but it seems to use hard limits.
Derakon I once implemented a limit on weak monsters appearing deep in the dungeon, in Vanilla. It makes massive, massive balance changes. Lots of the weak enemies in the game are also group enemies, which allows them to crowd out the nastier big guns (ever encounter a Miniature Cell vault with five acid hounds in it?). Removing them means that the "difficulty density" of the game goes way up. You'd need to tweak the spawn rate of enemies (both at dungeon generation and as time is spent on the level) to counteract this effect.
NerdanelVampire: Steamband gets really hard at the deep levels even though there are some relatively weak deep monsters. However I think I prefer this to leveled-up jackals of DOOM. I think a middle way would be the best, so that we would still keep generating weak monsters deep down, but they would be rarer than now.
And while this idea can be applied to monsters, I think items are the far more important thing to fix, as they are currently seriously broken.