We're doing almost exactly this with Bitcash (www.bitcash.org)
We'll have a reputation system. It will be peer-to-peer.
Proof of concept/MVP is at: trade.bitcash.org and our wallet is in maintenance mode.
The concern Hive account@blocktrades has is understandable, but I think for smaller volumes peer-to-peer exchanges will be fine.
My main focus right now is on this project. We use the Bitshares platform because it's easier to swap 1:1 between dollars for bitUSD and then go back and forth from Steem. I think you can do one just for Steem, but you'll be dealing with order books since Steem dollars don't hold a peg. Best.