They've made some attempts, the most notable was Sims Medieval which showed they could do something good with it, but sadly they ditched that one after one expansion and also painted themselves into a corner with the initial release which was a good game, but did not quite offer the possibilities people expected.
Still, it sold pretty well as far as I know, I still enjoy playing it quite a bit.
But I think they have a few pretty good options to work with, a series this big also has room for spin-off's. And I mean something long term that can keep getting expansions, not something to be abandoned after a year. Probably not as much expansions as the main game unless it sells as good, but just more content. A fresh direction, things they could not do with the main series which well, always ends up with a lot of the same stuff.
EA is also sitting on a lot of video game licenses that they can even use for this, either in full or partial.
So here's a few of the options that I think could have the potential to create something big, striking a good balance between familiar sims stuff along with fresh new directions:
It can take lessons learned from Sims medieval and combine it more with the love of different occult and other life states for Sims. Each neighbourhood would be it's own Kingdom with it's own theme, and each could always have a castle, A street with shops and guilds, a temple and some farms. Some jobs could be interactive, but for others your sim becomes an NPC. In either case when not playing them, you'd see them do their job.
The game would have some interesting new build options to build castles. Thicker walls, battlements, etc. Every thing would be made to look more medieval so buildings would look pretty different.
Instead of all sims being heroes, A sim can choose to be a hero, working on their heroic reputation in a similar way like fame. This could be part rabbit hole things like slaying beasts in a forest, but also winning a sword fight against someone of note, win a jousting tournament (yes there should be horses.) and all kinds of heroics that could come with perks, like joining a heroes guild which could have a quest board and could also erect a statue of your sim if they prove themselves a true hero.
This game could also revamp the inventory of sims to be more like an RPG. They'd have equipment slots, and you can mix and match there, and buy pieces separately. They could only wear a certain number of magical items at once, but crafting and or obtaining these would be something special, some could be unique rewards to unlock.
Each expansion could add a new fantasy race with a Kingdom where they live in, so fitting architecture, objects, etc.
Elves, Dwarves, Halflings, Orcs, Vampires, Fey, and of course different human Kingdoms are possible. They could launch the game with a typical western european Kingdom, a middle eastern one and a Spanish or Italian one for example.
Like in Sims medieval, it could have alcohol, sims being able to kill other sims and such.
Obviously, they have both licenses and it would work better on it's own than an expansion here. Would give room for all kinds of aliens.
Here each neighbourhood would be a planet. Well, a part of the planet of course, but in the select neighbourhood screen, you'd see the planets in the galaxy. And through expansions, more planets get added to that galaxy. With new species, building styles, objects, etc.
They could set it outside of any known time line, like create their own for it, but still have a lot of the familiar content, providing the players with the tools to create Luke Skywalker, Leia, Han Solo, Darth Vader, etc. if they so wish.
Death would be a possibility here too in adventures, but still quite rare. Like in a lightsaber duel between good and evil, or a bounty hunter getting their victim. Pretty much like sims medieval.
Sims could have all kinds of jobs, what is available could depend on the planet so sims could get a desire to move to another planet if they want a specific job.
Traits could be a thing, and force sensitive would be a trait so children could join the jedi order, or be kept at home. Could also be a Sith order to join the dark side. All force sensitive sims could have a lightside-darkside scale to show their allignment that shifts based on actions, and on this panel their force powers could also be displayed and skill with a lightsaber. Only force sensitives could use a lightsaber in this game.
Blasters could be for anyone though, but the game could have other traits that give unique options. Being an alien could give it's own unique trait that they always have. Like some can breathe underwater, learn specific skills faster, etc.
But you can have a nice family here too that does not live an exciting life of adventure. Like raise your little wookie family.
-Imperial age Sims.
Might be a bit more daring but I think there's a market for it. Elaborate clothing, powdered wigs, grand balls, being able to get your own (pirate) ship and decorate and alter it, your own movable home, or build a grand castle with fancy gardens, follow all kinds of trades which could mainly be rabbit holes aside from the interesting ones.
Since this is the sims and not actual history, there would not be any slavery or such, it's a fictional continent they would play with. With islands, a city, farms, and there could be indian tribes represented as well, working closely with people from existing tribes to portray them respectfully.
It's a great source for different occult sims like Satyrs, Minotaurs, Centaurs, Nymphs, Gorgons, Cyclopses, etc.
Plenty of interesting professions too like sculpter, soldier, priest, hero, sailor, fisherman/woman, merchant, etc.
Should certainly be room for greek tragedies too, some interesting possible deaths but also interesting rewards for exploring sims, could even be a labyrinth to explore with a Minotaur that your sim could try to escape from, fight, or befriend.
In fact, there could be multiple islands to explore, each home to another mythological creature and some sort of dungeon to explore. Each with unique treasures to find, but it could require skills to obtain them. Could be a little more difficult and deadlier than sims 3 world adventures, for the unprepared adventurer at least. Some traits could also help.
But again, you'd have both the regular family life and the adventure options.
I think that's key to the new experience, offer some more adventure and danger like in sims medieval, but while still offering the regular family life and going over generations like the regular series.