If the devs team made a The Sims Medieval version for the Sims 4, and make it according to what is popular for a medieval simulation games, all while adding in the Sims 4 flavors, this would be an awesome pack, or perhaps they could just make it a separate game the way they did the original TSM except, make it TS4 style without so much rabbitholes, and make it to where we don't have so much limits like the way TSM was.
Don't get me wrong, I loved TSM A LOT, but it was way to limited, and it the whole "rabbithole" issue was a bit of a controversial, what with people complaining about it so much in TS3 (well, at least I remember people complaining about it anyway).
This would be an awesome idea, none the less, and I really hope that the dev teams do try and explore this concept. Or at least do a community vote to find out if any of the fans are interested. I really LOVE when they do those votes for packs!