I think the potential for messy and incomplete athlete power curves may make implementing such a system difficult.
I actually think The Sufferfest might be on the right track with their “Half Monty” test, which there was a big thread about recently. It gives you a similar ramp test to TR, then asks you to cycle for 20 minutes at a particular heart rate (which will be a % of the max you achieved on the ramp). It then uses the power you achieve at that heart rate to measure your steady-state ability and adjust your FTP accordingly.
I don’t know if they have the data or the science to back up the number it produces, but the theory seems fairly sound to me.
Edit: alternatively, go the other way and follow the ramp test with a max 1min effort to determine your anaerobic capacity and repeatability under fatigued conditions…