jamestkirk, when you find yourself in a hole - stop digging!
Somehow I think you have missed the point here, and are trying to complicate something that from the outset is very straight forward and simple.
You cannot escape the fact that the 3 x rule works for just about every aircraft, including the "fast ones" that you may fly. Even at the perhaps not so fast 350 kts that I typically descend at it works perfectly, so much so that I rarely use the FMS to calculate a TOD.
As for pressurisation, and passenger comfort, the rule works well over all speed ranges as well. Those descending at a more modest groundspeed (un-pressurised types) will rarely exceed 500 fpm change in the in the cabin, while pressurised types descending at say 3,000 fpm will still permit passenger comfort due to the fact that their cabins typically have a TOD cabin pressure equivalent to not more than 8,000 ft in the first place - and therefore have less pressure change to make in the descent.
Sooty