I'm not understanding this logic. People use toothed ascenders to ascend ropes all the time and you are saying this is dangerous?
I have a pair of Petzl toothed ascenders that I use all the time, so I believe they can be used safely. Jugging puts a small load (body weight) on the ascender. No problem.
But imagine this scenario. Let's say you're leading 120 ft up your a5 route on hooks and rurps. Your last piece blows and you rip half your gear. As soon as you stop swearing, you find yourself even with your belay, but 10 ft away because it is overhanging, and you notice that you are hanging by a string of manky rurps. Do you slap on your toothed ascenders and jug up to your highpoint? What if the string of rurps blow?
There was that death in Zion in 2008 where the follower was jugging the haul line, 15 ft of rope slipped through the top anchor (improper rigging), and the force on catching caused the ascender to chop the rope.
As discussed, jugging a fixed line with toothed ascenders is fine (no slack), but falling 15 feet is not. Many people have used a mini-traxion for top-rope soloing, but there is little slack in the system so you don't free fall very far. How much slack is too much? I don't know.