I fly high power rockets. There are plenty of ways around the problems you mentioned if using commercially available single use or reloadable (You could even go EX if you know what youre doing) rocket motors. The ejection charge can be removed. There is now a commercially manufactured system for firing pyro outputs that is RC based. And no, rocket gliders are not always launched straight up. Our safety codes permit then to be launched up to 45 degrees from vertical. (Non gliding rockets must stay within 15 degrees of vertical.) I'd recommend using a separate channel to light the motor. And remember, that motor exhaust is HOT. You should laminate the plane around the nozzle with either Kevlar or Nomex-Kevlar is better cause its stronger. That motor is going to kick the plane pretty hard when it comes up to pressure. When i get around to doing my RC boost glider, im covering a sailplane with carbon fiber instead of that thin plastic stuff. Also, a true model rocket will not fly sideways. The fins dont create enough lift.

William