Been away for a while with other projects and noticed that the Epic marketplace is gaining a lot more traction which is AWESOME.
One thing which came to mind and I found a thread started about it was Distributing source code with user-created plugins?
I think that if Epic could streamline the process for developers to link marketplace content to github (or other source management providers) similar to how UE4 was initially done via subscription (before @TimSweeney decided to give UE4 away for free (Thanks Tim!)) this would help a lot of users to be able to collaborate with each other and build a stronger community.
For example, developers who are using the RTS toolkit would like to be able to have multiplayer support, but the developer is too busy at the moment, so by being able to release their source on github to paying customers who may have the time to implement the necessary changes, everyone benefits.