You are designing smartcontract based exchange.  That would be good.

But when a user submit "bid" or "offer", it is only 1 side of a contract.  How will you match up the parties to actually create a full transaction?

Will you show the depth of "buy" and "sell" orders?

What happens if I want to buy or sell on the market?

How will you stay in business with no fee?  Get the money from the ICO?