I understand what you're saying about the testing world and the file size reasons. However, as there's barely anything here at the moment, I'll refrain from playing this in the current state, but I'll see how far you get into actual development. A lewd Fallout / Borderlands - style game would be amazing to play, since I've always wanted to mod the heck out of Fallout to make it lewd, but couldn't be bothered to mod it properly after doing so for Skyrim and then losing my mod list because I swapped computers.
If it turns out anything like you have envisioned, this should be a nice compromise. Especially since it looks like you're aiming for mod support for this game, too.