You mention that you might have plans to introduce an exchange on the website. I think it would be best if this was avoided to prevent conflict of interest. Although if you think that an exchange is definitely worth it I would strongly recommend keeping it separate to the marketplace.

One of my main concerns about the exchange being a part of the marketplace is people keeping their tokens on the exchange and using it in the marketplace and if the site was breached then both could be compromised. Where as if they were separate it would be more secure.

Might I ask what security features the marketplace will have? 2 factor etc.