A very simple one...practically useless....Low speed the stick needs to come back a long way, high speed you pull it back a short distance too fast and you stall the wing (if they don't drop off). So where do you paint the line? right at the back, or just aft of centre?
Yes, and it would also depend on both the trim and C of G.
It's right in spirit, though, in that the real function of the elevators is to control the angle of attack of the main aerofoil. Just how much elevator deflection is required will depend on speed, as englishal says.
The other thing is that AoA info is not just useful for detecting proximity to stall, but also for flying at best rate and best angle of climb and also best glide.
QDM