I searched but couldn’t find any threads talking about how to handle packages that are dependent on other packages also available on the marketplace. To keep things simple and flexible I would personally like to have the ability to require users to purchase those other packages created by other users before they can purchase mine. This way, if needed, I can package their work with mine in a way that would benefit the other author.
One example would be someone makes a voxel terrain plugin and I am making an adventure game example package that requires it. Or I make a FPS game that requires a character model, weapons, and an inventory system that I got from the marketplace.
This is something that was pretty annoying to deal with when working on Unity Packages. It would be nice if UE4 could nail down a solution early on to deal with it. I would really promote collaboration in the community as well.