hitreg/netcode optimizations would be lovely, although hopefully that will be better if the game gets ported to source 2.
fix random floating hats and unusual effects
You can still get stuck on many things in the tunnel on pl_upward.
Also I might be wrong on this but pyro airblast was never intended to kill all momentum (?), so how it functions now should be considered a bug. It's really frustrating fighting one and then you get airblasted and you can't strafe at all and it's just dumb. Having airblast not take away all your aerial momentum/strafing capabilities will make it less dumb to play against.
Edit: also default sniper crosshair is noticeably offcentered and so is the default scout crosshair (by like a few pixels). Will it ever matter? Probably not, but it's still silly that it exists in a game as big as tf2.