Machine guns are very powerful I can agree with that, but the assault rifle is still a better weapon at most ranges imo. Snipers are powerful but generally only on games with the low health option on, and even then you can often out snipe them with an akoban.
I think it would be a bit of an head ache trying to make the machine guns more balanced as you call it, I mean, they are supposed to be powerful, high rate of fire with large amounts of ammo, accuracy should be poor, and that for the most part is how they are... I suppose accuracy should be a little worse though, they arnt far off of assault rifle accuracy.
I agree that there should be a game type with bigger maps, Like a whole rush map to fight over, because as you say generally the maps are a little restrictive. I still really enjoy rush, though I find 16-24 players much better than 32 player. 32 player is just too much really, stick your head up and its pretty much gone
I still think its more balanced than MW...