I like this belt idea. New thing to farm, upgrade etc.
I assume there will be new section in Auction Hall as well.
This new section also focus the question about inventory / stash size.
Inventory of 500 is more-or-less OK especially if we cannot group items (now different types of Lockeds, gems, energy kits, etc)
BUT 250 space as stash slot seems a bit low. I feel that 500 stash slot would be sufficient.
What do you think?