I would certainly take my chances with being unable to isolate an electrical system
Which rather implies that you consider the risk of hijack on any given flight is more severe than the risk of electrical fire on board. I am not sure that would stand up to statistical scrutiny, probably by a factor of several thousand - even if the "no-off" transponder was a sure fire deterrent of hijack, which clearly it is not.
The mystery of MH370 is frustrating, but perhaps it is better to just swallow that frustration than fit an additional fire hazard in every commercial aircraft just in case it happens again.
As for psychological profiling, I am similarly sceptical about its effectiveness. But at least it is directly addressing prevention. The transponder issue is just helping us find the wreckage afterwards.