In Starcraft 2, you can not-mine Vespene Gas and still build a few units. These mineral-only units don't stand up too well against tech units but there is something you can do which counts if you did enough damage.
I suggest to give options during power stalls:
- T1 tanks and T2 non-amphibious tanks cost no energy
- Mass extractors require no energy to run
- T1 power generators and hydro cost no energy to build
Obviously, energy costs for other units may face some rebalancing work.
Which nobody might do, but I want to make this point now at long last.
So if you destroy someones power grid expect a massive tank push... have your gunships ready or whatever.
Also to recover from power stalls less gruesomely the T1 power generators should cost no energy.
Power stalling will still be bad, but not so stupendously punishing as it is now. I have never seen a mechanic as punishing as the power stall in any game. It would be as if Protoss could only build pylons in a pylon power field. As if zerg don't get larvae if they are at supply cap thus rendering them unable to build overlords without suiciding units first.