I think with the current ballistics being what they are and the complete lack of differentiation between aiming difficulty between a handgun and an M16 (for example), a machine gun isn't necessary. You can get yer 'suppresing fire' thrills from the P90; not like anyone would want suppressing fire anyway.
With the current gameplay somewhat failing to enforce teamplay, I doubt that it's really necessary. If you got out there with something heavy like that you'll get pronekilled or naded right away.
I think SF with its horrid unrealistic ballistics, improbable damage model and horribly slow running (well, more like arthritic jogging) actually promotes better teamplay than INF does right now, simply because you're so slow walking over a more open area that you WANT cover, dammit

And it's so hard to hit someone that you NEED backup to take the other guy down faster than he can take you down.
I think INF is more of a twitch-fest right now...who can prone faster, nade faster or squeeze the trigger faster. A team will get naded more often than they suppress someone, 'cuz how do you suppress someone that runs faster than your team, runs around you completely and takes out your entire team (which is carefully trying to advance) from behind.
As such, another pistol would be good, esp. silenced so they don't even know what's going on
[L]-Damodred