I've used multiple shopping cart frameworks (a lot of them broken), and my favorite (which just so happens to support multiple vendors) is PrestaShop. It's free, open source, and suppports all that you asked for. Is this the framework you were looking for?
The Wikipedia page you cited lists multiple vendor support as a column in Other Features, along with features that are pertinent to your search.
I cant really gove you an answer,but what I can give you is a way to a solution, that is you have to find the anglde that you relate to or peaks your interest. A good paper is one that people get drawn into because it reaches them ln some way.As for me WW11 to me, I think of the holocaust and the effect it had on the survivors, their families and those who stood by and did nothing until it was too late.