Im thinking on similar lines - just wrote a redundant topic over at
https://bitcointalksearch.org/topic/yet-another-decentralized-exchange-topic-173187I feel that Ripple might be a bit heavyweight, and that a simpler solution ought to be possible. Having to establish social connections just in order to buy 10$ worth of Bitcoin seems to me like too much overhead for the average consumer, at least for now.
I like the idea of 'minting'. Where some provider can establish him/herself as a clearing house. The provider will give out tokens that are tied to a local currency amount, these tokens can be used for P2P trading and then later cashed-in.
Basically we can decouple the establishing of Bitcoin trade contracts ("I buy 10 btc for $2000" etc) from the handling of fiat. The former can be easily done in a P2P manner, the latter not so much.
I was also thinking about the 'coloring' of coins over the existing infrastructure:
Following on from the 'colored coins' idea, where we represent some subset of Bitcoin as having special value, what about ...
- MtBox maintains a special Bitcoin address, any coins that originate from this address are considered special.
- Anyone can see if a coin is of the MtBox colour and ascertain its true USD value.
1) Bob sends $10k to MtBox
2) Bob creates a Bitcoin wallet
3) When satisfied, MtBox sends a symbolic and tiny amount of Bitcoin to Bob's address. This symbolic quantity of Bitcoin will represent a specific USD amount.
Bob can then send a certain quantity of his colored Bitcoin to a seller for 'real' bitcoin.
4) The seller can send the received colored Bitcoin back to MtBox.
5) MtBox checks the transaction history of the coin, ensuring that it is indeed of the MtBox color
6) MtBox calculates the appropriate USD amount and credits it to the Seller's account.
Anyone could act as a colored coins provider (though legal issues may arise). It would be up to the market to decide which providers to trust or not. We would see differing exchange rates between say MtBoxUSD/Bitcoin and say ZhouTongUSD/Bitcoin, according to the risk factor!