Ernie even easier. BuddyPress + a theme that integrates buddypress and wc vendors such as Onesocial Marketplace, or BuddyPress + our integration code found in our knowledgebase.
Then, vendors can message customers and vice versa on your website. Add a standard buddypress message attachment plugin (free, wp.org) and voila, now your vendors can accept orders, and after payment continue to talk to the customers and send / receive files.
Gravity forms would probably be highly unnecessary, unless there is some feature you need that I dont know of or for some other purpose also on your website. But for this exclusively, would be a waste.
Cheers