I remember working on another power scale calculation thread a while ago, which calculated not only raw power but things like cleverness, connections/alliances, limitations, and territorial advantages. So it ended up being closer to a danger scale instead of power, along the lines of "it's safer to piss off Mother Winter than Lara, because Mother Winter (probably) can't directly do anything to you, despite being way stronger than Lara".
In any case, though, any power scale calculator would have to have error bars implemented, and I suspect they'd be large enough that any comparison between reasonably similar-tier characters (as in, not Butters vs. Ferrovax) would have overlapping error bars, and so the scheme would be very rough regardless.