from my perspective, reducing airbrakes at 100' changes your glide slope and therefor aim point half way through final. So do you give up your initial aim point at 100', or do you have two aim points? Either option seems like a bad idea for students.

Airbrake deployment should be a driven variable to maintain a correct approach, not the other way around.

Additionally, a shallower approach for the last 100' means you are way more susceptible to wind shear, as you don't have much "extra" glide to recover by closing the airbrakes.

To me, it sounds like the tail strike problem is in the flair, not the use of airbrakes.