Designing an airbag compatible bumper takes a lot of engineering time, but if you are aware of the issues, you can at least decide whats worth doing and whats not.
The issue you will face with a stronger bumper is early airbag deployment. That is, they may go off during a collision at a lower speed than intended. The deceleration in an accident will be quicker since there might not be enough material crumpling and absorbing energy, so the vehicle will think things are happening faster than they are.
My suggestion would be to design something that will protect the vitals like the radiator and be stronger on the outside corners. Don't focus on reinforcing the chassis too much, but give yourself at least three points of connection on each rail.You want something that will deal with animals, trees and fender benders, not a battering ram.
