I totally agree that I would like to see more pre-tech and magic/supernatural/mystical type stuff. I am behind that all the way, 100%!
However, for a Pack that makes use of all current worlds and functions, I would LOVE an "Accessibility Pack"! Let Sims have hearing aids and mobility devices- I'd love to see Sims getting around with wheelchairs or walkers, or blind Sims with canes or (if you have Cats&Dogs) a service animal.
Relatedly, service animals for Sims with epilepsy or anxiety (or PTSD- some of the things these Sims go through is extreme, I mean, watching your friend burn to death in your kitchen? Yikes!)
Build Mode items would be things like wheelchair lifts for stairs, both interior and exterior, or the ability to create ramps in place of stairs.
Shorter counters and cabinets for wheelchair users too. Alternately, this would also be a good time to implement the use of elevators in user built structures!
Sims with hearing aids can have actions like "Turn off ears" when in a frustrating conversation with a Sim they don't like, or a debuff for "old battery" for a stress factor- not being able to hear because you forgot to replace the batteries is godawful, or so my Nana tells me!
Hand animations for Sims who use SSL- Simlish Sign Language. They can have a hidden trait- "Knows SSL" or "Doesn't Know SSL", and can choose to study SSL from a book in the bookcase or from studying with an SSL speaking Sim.
Basically, I think a Pack that makes the Sim world a little bit more colorful and inclusive would be WAY cool! Some animations would likely have to be adjusted (kissing, hugging between a standing Sim and a Sim in a wheelchair for example), but I really think this sort of thing could be great!