I think that being able to 'favourite' specific projects, and have them in a list (or multiple) for later reference would be a good idea, for buyers and sellers alike. Buyers, obviously, would be able to make a list of projects they like, that perhaps others could see, and that they could come back to later, for when they're ready to request a project. 

If lists are visible to the public, rather than private, than that could potentially be further exposure for any seller who has had a project put into the list. Although, I imagine people may be interested in a private favourite list, too. This is actually something I thought to myself, looking through the feed and following different artists. "It would be great if I could take all the project listings I liked and put them in one place."

However, then you might have to think about what would happen to a project in your list, in the case that it's deleted or changed to 'unlisted'. I imagine, there wouldn't be any notification and it would just vanish? Or maybe have some notification that a project has become unavailable? ^-^ I'm not too sure about the finer details or what it would take, because I don't have any sort of website building experience, but I'm sure that others may find a "Favourite Projects List" useful!