Honestly, I can see this game being ongoing with how many possible scenarios you could make from this VN's concept. While each character might end up having 10-12 levels (split between muscle and fat), and will certainly add more work to the table, I can see the list of characters and locations in this game expanding for however long you want it to be.
But that's just me. I imagine there's a finish line somewhere for this project, but regardless, I do see a lot of potential for this VN in particular, as a writer for this kind of TF stuff myself.