I think that it would be really usefull to have a rotatory menu like L4D where we can call for a medic, taunt other players and basic things like that. I guess that it was already suggested but suggesting it again won't hurt...I guess..
I would be happy with a voice chat system that worked. Since everyone already regenerates health calling for a medic like in TF2 would just be an annoyance. You can already taunt press G.
a medic call on heavy classes would be useful last night i was playing gunner after playing some tf2 i ran back with a tiny amount of health left a support next to me did nothing i started to mash E (which calls for medic in tf2) and was like oh.... not tf2 medic button