I would have it act slightly like support in MW3, when you die you keep 20% of your score. That way it has value but only if you're not dying a lot, therefore making balanced. I got the 20 percent idea from hardline, because they sound similar.
Countering EMPs completely was a decent buff. I use EMPs as a sort of radar, if I get a hitmarker I know someone is in the area. You no longer get hitmarkers on somebody using hardwired, so they can camp in a corner safely, knowing my EMP didn't give them away.
Permanant MW3 Jammer effect. Not sure what radius is fair though. This way it would kind off counter vSat. The enemy would know where you are until they get within your immediate vicinity and it would be a silencer alternative. Perhaps it could also protect equipment in it radius from being destroyed by EMP nades.