Item Stacking.

[Karbuncle]

I would actually just enjoy the prospect of certain Items Stacking at all.

Potions, Ethers, Etc. I know we have "Drops", but those Medicate and were just... well they Medicate. I think a "Tiered" Stack system like you suggested in the OP wouldn't be a bad idea.

Being able to Sell Stacks of Items as either 12, 25, 50, or 99 Would be a good, But It makes me wonder how much programming that would take to Alter Auction houses and the like.

Though, I think when they mentioned adjusted certain items to stack, They were talking about Empyrean upgrade items (Glavoid shells, Etc), I Might have missed something , Or i'm out of the update loop though.