> It's probably reasonable that radio hardware can't trivially be reprogrammed to exceed regulated power limits.

No more reasonable than limiting cars to 75mph (which some people, admittedly, are probably in favor of).

I think an 80mph limit would be reasonable (10 over the limit in the UK).

I wouldn't be in favour of a hard 75mph because current speed limits are set by social consensus on the basis that they aren't strictly enforced. The police are extremely unlikely to stop you for doing 76mph in a 70, so I don't think your car should.