I'd like an open world again, and be able to edit it in any way I please, maybe even place new roads! I'd also like amusement parks, airports, and a way to own several buildings and companies, and then rent them out. I'd like to do a playthrough as a mob boss sometime. >:D
Probably a very small thing I want that is a bit of a far reach, but whether it is a DLC or not, I want dragons like in TS3 Dragon Valley, but this time make them eventually grow up, and have more interactions than just "feed", "talk", and "ask for magic". Maybe make them be able to live in big bird cages when they're babies so they're not just strewn out on the floor all the time. Being a big dragon lover, I felt like the dragons were so underwhelming in TS3...