Great idea, but how would a first time buyer of BTC provide any collateral. It would just be a scammers haven without some sort of escrow agent.
Either get some BTC form other exchanges or faucets or use a non-collaterated offer. If a reputation system is included he could use that for minimizing the risk of fraud when doing a deal without collateral. Note that even without collateral nobody can steal money of the other, they could just be evil to not continue in the process und not unlock the tx. they would not win anything but the other would loos something.
For very small amounts (10 USD?) I can imagine that that risk can be taken.