I'm sure that I'm not the first to mention the idea of super powers in the sims but hear me out:
A metropolis type city with new types of jobs as "origin stories" I.e. Journalist, Genetic Scientist, Nuclear scientist, ect. a few days after you start the new "origin story" your sim gets into an accident relating to each "origin story" your sim develops a new skill called something along the lines of "super powers" or (Super power name here) some powers. as an example the journalist investigates say a new museum exhibit and gets bit by a prehistoric mosquito and develops the skill "Dino Strength" they can train their newfound skill by using a Super Sim Training Kit. Once you get the super power the "origin story" job ranks up into some kind of super hero job line, at a high enough level of job it can split into two path's offering a super villain line and a Professional Hero line or something of the like.
other smaller stuff:
you can now build secret doors out of stuff like book shelves and fireplaces that can be used to access a secret lair area or even just be able to buy a mansion or house with a secret lair under the house.
your sim can make another sim starting from age teenager and up into a side kick or henchman.
your sim can open and run a comic store and browse the internet looking for comic books to trade and buy and can even make their own with the writing or art skills.
your sim can reveal their secret identity to sims they trust but be careful! talkative sims will expose them causing your sim to be embarrassed for a few days.
New clothing items including masks and super hero costumes. you can even make a disguise for your sim so perceptive sims won't get suspicious of your sims secret identity.
New objects like costume display cases for sims to show off old costumes and attire. super trophy cases to hold collectible items and villain gadgets and even a Super Sim Super Computer which they can use to access hero work from home or become a powerless free lance hero.
Tinkerer sims can make a handful of super gadgets like a smoke bomb and a grappling hook with the new Super Sim Gadget Bench or even make their own costumes on the Super Sim Costumematic.
Super Sims can even develop wacky weaknesses such as cheese or a special kind of rock.