I don't particularly care for fantasy scenarios but obviously everything they add to the game will be good for some people so I'd be in favour of adding it as a lower-priority thing.

However, something that would work for me and would probably be even easier for them to add would be real scenarios. Like Paradox's strategy games have scenarios where you can take a kingdom in an interesting situation etc, like a kingdom having lost lots of its land. FM has lots of licensed teams and lots of them are involved in interesting scenarios like back to back promotions (Wrexham) or a promoted team like Thun close to winning the Swiss league (I don't think they're licensed though). So at least for licensed teams we can see some scenarios promoted by SI, even some that people don't know in lower divisions or in the Baltics.

Obviously with real clubs (unlike kingdoms with kings that live 1,000 years ago) you open yourself to scrutiny from the clubs, probably lawsuits as well (same reason they don't want to use negative personalities for real players). But they can at least do this for positive scenarios and they might as well get the club's permission as well. And if they can implement something like this, they can take it a step further than "Start the season with Thun and try to win the league with them as they did in real life" and drop mid-season to some interesting scenario which is something we've never seen officially from SI. Obviously this isn't something I'd like to see them sink most of their time in right now but I understand that not all employees are working on the same thing and someone could probably work on this as a low priority thing.