MiniVend can share product databases, session files, and any other databases. It has many features which support mall building.
You can easily build separate and mostly identical catalogs which you link to via HTML.
But building a mall is as much an exercise in data and process as in software. Consider the following questions:
Who will be clearing payment?
What happens if everyone doesn't have the same tax rate?
How will you clear orders to multiple vendors?
How will you bring together multiple types of shipping?
How will the vendors get product data (including images) to you?
If you cannot answer those questions and then visualize how to build a mall, then you probably should not try.