A schools pack with the option to send the Sim to private school or boarding school, prom and graduation for teens, and a lot of after school activities.
A fairies pack where we can choose our fairies wings, colour and powers. Allow the fairies to go into a small form and give them unique interactions.
It would be nice to have genies too. An advanced wish system, the ability to set free and play as a genie, and give genies unique abilities.
A hobbies and sports pack where we choose our Sim's favourite hobby and sports, they develop interests and their interest grows the more they engage in that activity. The interests could be cooking, arts and crafts, sports, TV, music, reading, magic, etc. It could add new activities like sculpting, and sports like archery, volleyball, tennis, badminton, cricket, etc. They could join a sports team that will work like part time jobs. These could include soccer and Ping Pong (if you have Discover University), basketball (City Living), and bowling (with bowling stuff).
My first 2 ideas are probably game pack ideas, and the last one is probably more expansion pack size.
