Game Episode Launcher?

I'm trying to figure out a way to package our game episodes into one launcher, in such a way that people can purchase and download / uninstall each episode.

For many many reasons I will not get into here, it is simply not feasible to "merge" all the episodes into one product. The chief reason being that we've already developed the episodes in separate Unity projects and cannot combine them without going through a lot of meta information hassle.

Is there a simple way to make multiple discrete Unity projects packaged and launchable from a shell application? I'm tearing my hair out and I can't seem to find anything useful on the topic. This is specifically for the iPad but a general solution is fine as long as it works for all devices.

 

Alternatively, is there a way to unlock separate games via in-app purchase? From what I understand IAP is usually reserved for internal additions to a game, but can it also be used to allow them to purchase one or more episodes from within the game so as to unlock those episodes on their iTunes account?