As long as commercial transport pitch control systems are designed such that loss of adequate pitch control is extremely improbable, I doubt that there will be any value seen in designing engine controls in such a manner as to provide backup pitch control.
There have been more than you think occasions where thrust control saved the day. The loss of pitch control was not a failure of the pitch system; it was because of an external cause such as a mid-air collision or explosion on board. Totally unpredictable. It's happen many times, going back to first time I heard of this demonstration of great skill on a Constellation that had 2 fins and most of the elevators chopped off. Sods law is still in force.
I thought an F16 (FBW) had demonstrated this system and then a B727?? Someone will know for sure.
I suppose it will all come down to risk assessment and cost v risk.