These are just suggestions of course, but the second one is really important to me.
Turn based or turn-based hybrid. As long as I can order the party around while "paused" I'm happy.
If you give me a party of 20 people, I want to be able to have all of them with me. Why would I leave 14 of my dedicated warriors back at camp when I am already facing impossible odds? Is it because I'm stupid? Yeah, must be.
Magic is magical and weird and awesome, not a replacement for grenades and napalm.
Lean more on tactics and interesting character builds than on fancy equipment. If I am a superlative warrior, I should still be formidable while naked and angry.
Classes a la carte.
Stabbing enemies in the eyes is a viable and hilarious tactic.