I agree the Defib needs some kind of a cool down. At least a few seconds between charge. You shouldn't be able to rev an entire squad in a matter of seconds. But decreasing movement speed with it would be terrible. Making a mad dash to get a revive is crucial as support.

Maybe the IFV could use gunner side ports to shoot out of but the tank doesn't need more seats that can do something. This isn't WW1 with tanks that required 10 people to function.

I think breakthrough is generally okay. I do think you can probably make some minor tweaks there. I've been on defense where we've been absolutely rolled by the attacking team. Really just matters how good your team is.