If that's the only problem, it shouldn't be too hard to limit either in hardware or have the HW run the user-provided firmware in some rudimentary VM that essen

If that's the only problem, it shouldn't be too hard to limit either in hardware or have the HW run the user-provided firmware in some rudimentary VM that essentially passes through everything except the commands that set TX power; that way you maintain compliance without restricting people from running their own software. I think however it's just a matter of time before these restrictions become obsolete anyway: 1) I'm not sure whether the possibility of violating FCC regulations is something that will be used in practice by enough people to be a problem (you might get the odd one out here and there, but see the point below) 2) People who intentionally want to violate FCC regulations can already do so in plenty of ways - SDRs are becoming cheaper and cheaper and there's basically no way to prevent their import, so I'm not sure why they'll even bother with a wireless card if their aim is to truly cause mischief and shit on restricted radio bands.