Is there any way to implement those charge-up pips like on the EMP tank in TS?
No, not that I'm aware of. PipScale=Charge doesn't work in RA2.
You can use an ammo system to make one pip appear if its charged, and be empty if not. Doesn't give much of an idea as to how long is left to charge, but then it doesn't give much idea of how long is left to reload aircraft either.