You're going to run into reverse transaction fraud if your customers are allowed to use anything other than wires or certified payments. How will your company handle that? Will you have a CIP/KYC program to go after customers that abuse the system and/or are your transactional fees just atrociously high to manage the risk? Your 10 bitcoin deposit requirement seems too weak to deter sophisticated fraudsters (of which you will be inundated with).

What happens if the seller simply says the buyer's money never arrived and asks for his bitcoin back from your company? Can your company independently verify receipt of payment?

Also, logistically speaking, how will this work across different countries? It can take days for a transaction to clear, in which case the price of the bitcoin may fluctuate wildly and buyer/seller may no longer be interested in the transaction.