Example
Mister X needs to pay his electricity bill with crypto. He posts the bill data to the site and the crypto he wants to pay with. Once someone wants to buy crypto they simply pay the bill for mister X and they get the crypto unlocked in the escrow.
with this example, you just want to be a middle-man and charge fee on the transaction?
why not just establish a business type of payment service, accepts crypto and makes fiat payment on customer's behalf?
next you just need to sell your crypto balance to refill and keep enough balance on your fiat account
you need to do some good book keeping to maintain good cash flow and to time your crypto selling for maximum profit