Deuce-Six, the scenario you describe is why a lot of Elcans have vestigial irons mounted right on top of the optic. Glass gets broke, move your head a little higher and drive on.

Frankly, if I have the luxury of time to KNOW I'm going into a fight, I'm grabbing the FSB M4 and deploying the rear BUIS while I move to engage so that even if the Aimpoint takes a crap the iron's already there. C.'s C8 is set up similarly based on how a Canuck buddy set up his in the Rockpile, with the CF-issue plastic fixed sight at the very rear of the upper and the Eotech up front raised for lower-third so it's "adjust eye position and get back to work."