You somehow assume humans are like clocks and can be there at predictable times all the time. It maybe somewhat works for full time paid employees (though now that remote jobs taking their foothold it changes more and more) - but I fail to imagine how it could work for game where people do it as some voluntary unpaid duty at their spare time. I do not think it really works.
So actually, I would be positive even about another one or few US GMs or so as long as person fits this position. It would "improve overall coverage" in average.
As for rules and enforcement... well, GMs were nominated and elected by community - so they have each and every moral right to apply their judgement on community members. Community explicitly delegated role and have to face results. However, nobody elected admins or devs to do that. At which point I can imagine it only should be used as "last resort" if normal GM means fail in some weird ways (like that crazy moron Pateame, etc). Otherwise ... devs and admins do not really know community and what's goes on - none of these are active players and so they don't really keep their hand on pulse. Any intervention is delicate thing, it easy to get it wrong. Pissing off some players in process. Say, some devs driven some captains of my guild out of gameplay. Notice, I say "captains". It means more than 1 person got upset and left us. Despite taking exciting position in community. So when someone is about to use "elevated" commands, they have to understand one simple thing: power comes with responsibility.