there are very few banned accounts that have anything of value on them now, we cleared them ALL a very long time ago. i'd guess the account you are talking about is Gabriel, he was banned at least a year after we'd stripped all the others. i expect his items will be harvested at some point.
of the newer breed of banees, pretty much none of them have accumilated any items that others would lust after, it was the old guard who had inventories full of rares.
occasionally we might free up the name of a banned account; if someone requests it, and it wasn't a prominent user, but I'm not sure if you've considered what you're suggesting with regard to releasing
all banned usernames, there are nearly 8,000 banned accounts