There already is a kit for bathroom items. We have toilet rolls and sundry to junk up a bathroom counter and/or dresser. All kinds of goodies, if you will. Hair dryer, et al. Not saying they're playable, but they are there.
But I do agree a pack with more formalwear for our gentlemen Sims would be a very good thing. I currently have a Rock Star in my game who is a clothes horse. He doesn't like to wear the very same outfit to the Award Shows. Can't say I blame him.
New instruments in the game would be long overdue. We had more in Sim2 then we have now. I would also appreciate the child sims being able to play more than just the piano and violin. Guitar comes to mind or even drums, should they ever bestow that upon us.