I'm building out a pet project webapp called CollaboTree, a big part of it is allowing users to set bounties for completing/collaborating on little bits of work. I'd like these micro payments to be as cheap/free as possible, and fast (instant?) would be good.
Would it make sense to:
Make a wallet for every user on signup, and make all internal payments go onto the blockchain between real wallets
allow users to load/unload bitcoin onto their accounts to some kind of shared wallet which only the app has access to, then maintain a balance for each user in database letting them transfer among themselves instantly outside of the blockchain, then letting them get their coins back 'live' when needed
Have one big wallet for the entire app, with each user having their own address which is the only one they can spend from or something?