Ok, so maybe you are suggesting that the engine be replaced with one using pre-1970’s technology. That might be a wise thing to do. The tank would then have the power to not only move but to fight. Assuming there is a backup targeting system installed.
There isn’t a single pre-1970s tech engine that can fit in the Abrams that will be able to move the tank at the current speed and acceleration requirements.
The Honeywell/Lycoming AGT1500 used in an Abrams makes 1,500 hp and 3,950 lb-ft of torque.
Additionally, NO piston engine could meet the multifuel requirements. The British came closest to doing it, but their Leyland L60 turned out to be a giant disaster. Nobody else even tried.
Absolutely. Guaranteed immunity to EMP. And in a pinch, when all of the other tanks are dead, you can still move. That is a huge plus.
And your basic engine hasn’t changed much in the years. Basic engine tech hasn’t changed at all. Still spark, explosion or glow plug, thermal expansion both via timing. An engine still goes bang.
So, fundamental systems that determine survivability must be able to continue to run and operate. This can be done through redundancy or default and drop to a simple state.