Right now I just want them to do two more things: add Solo and to make future classes free. I do not like having (gameplay altering, and do not tell me best boi Mirage is not gameplay altering!) classes behind a payment. I'm sure they'll be doing enough with the cosmetics and season passes.
Solo would fundamentally alter the game on so many levels as to cause big issues.
So much of the game is designed around and predicated on team based play - one of the shoulder buttons is exclusively a communication tool. The revive and respawn mechanics. Legends like Lifeline or Mirage who have abilities that only work on downed allies or being downed.
That's not even taking into account legend balancing. Some would be OP in solo (Bloodhound) some would be very much less so.
I genuinely hope they don't alter the game too much too quickly based on knee jerk reactions. Deathmatch in Overwatch sucks because taking team-based classes from a team based game and throwing them in a single player mode doesn't work. And it wouldn't work much better here.
Apex is very much designed, from the ground up, around fireteams.