10 kills for the plasma
25 or 50 kills for the megaposi

The megaposi is a great multipurpose tool, but I next to never use the plasma or see it in use. Else, buff the plasma

They already did buff the plasma annie, it's pretty awesome now. It's supposed to have concussion making it the only energy weapon with concussion (i.e. the only weapon without ammo that has concussion), but the game engine handles that differently. Incarnate committed to making sure it works next time they review that particular part of the game so it was previously buffed and it's got a slight buff in the future planned.

Yeah it's actually a good weapon now. I use them all the time in Deneb.

I was a fan of the Annie before it was cool.

As far as reversing their unlock levels, the MP is an easier tool to learn, so it should still be the first reward IMHO.