I'd love a pack like that! Being able to make gameplay scenarios for other players to make their way through sounds like a lot of fun. Then again, I may be a little biased because I'm both a writer and am currently making a full JRPG in RPG Maker MV...But, just imagine the possibilities! The tales we could tell, the puzzles and dungeons we could design, the incredible boss encounters that we could engineer!
These scenarios could come with NPC sims we make to serve as enemies or informants, multiple locations and bosses...Oh, this pack would definitely have to come with a world creation tool too, so we can make worlds and neighborhoods to fit the needs of the story. And, of course, they could possibly borrow from the Spore creature creation system so that we could create our own boss monsters! EA/Maxis owns the tech. If they could integrate it into TS4's engine, that would be just...awesome...