Really, I'd combine medieval and magic into one. I actually like storylines quite alot, it's perfectly acceptable to me to have a semi-linear storyline sprinkled into the overall arc of my sims lives once in awhile but I'd rather have something a bit more ongoing besides the main story, it's all well and good to have that in a game but there needs to be side content
Strangerville was different, and some people don't like that, I thought it was great personally besides it being something you just play through and then it's over.
So say they have the main storyline that you can deal with in the new town, hunt the big bad, protect the realm, etc, but eventually you are going to have to settle down. They could have various threats pop up now and then (vampires, werewolves, dragons, witchy cults, etc) for you to go out and deal with similarly to Strangerville or jobs like detective where you travel to a scene, find clues, and eventual confront and deal with whatever the threat is
Steadily moving up in the world as you do so like a profession.
Just because you deal with the big threat doesn't mean that smaller ones don't happen.
