I think a good brake would certainly help. You would still have to be prone to do any good, but if I had to fire a full auto M14, then yes I would want a brake on it. With that said, I have a SOCOM 16, and the factory brake doesn't seem to do much for recoil. Not really sure about muzzle rise, I haven't shot it that much. ETA, it's really more of a comp than a brake.
As for machine guns, they have their place for CQB work. A high quality submachinegun might be the most effective self defense weapon ever devised. That or a 14'' shotgun. Think full sized Uzi or MP5. I for one certainly wouldn't mind having a Kriss Vector next to my night stand, that's for sure. And I would love to have my PS90 converted. That thing with T6B and a fun switch would absolutely dominate a CQB kerfluffle inside my house.
What gets me about the whole machinegun debate is this. The liberals tell us we don't need them for home defense. That means us, by ourselves in our underwear half awake, against an unknown number of intruders who might be armed and even wearing body armor. Yet, they're absolutely required for someone with an entire SWAT team backing him up, even in situations where there's only one occupant. And this is the big one; they have the element of surprise, whereas you're the one caught offguard in a home defense scenario. These are mutually exclusive ideas. Either submachineguns are needed for self defense in close quarters or they're not. They can't keep having it both ways. If you can make the argument that an SMG is good for LE or military, then you've just made a better argument that they're good for home defense.