Umm, why do you want to put CO2 through a HPA regulator???
If you want to destroy a Govnair, just hit it with a hammer or something, it'd be a lot safer and a lot less effort.
The reg would possibly 'work' (in that you'd get CO2 out of the output) for a very short while, but would then be totally knackered from the CO2 freezing the seals and o-rings.
As for threads, no idea - it's been too long since I owned either a Gov or CO2. I vaguely recollect that the Gov had an odd thread compared with other air systems of the day, but that's about it.
Technically you could rig up a hose to put through CO2 through a fill nipple, although how reliable that would be is another question.