What would this EMP proof power source be? Is such a thing even possible? Now if one gave the crew the ability to go old school by being able to manually transverse the turret, change the elevation of the gun, manually fire the gun and optically zero in on targets, at least the crew would have some ability to continue to fight.
Power Source — depends on how much of it is electronic. An EMP destroys electronics (semiconductors). EMP shielding is designed to protect the electronics.
Also, maybe it is less important to be able to continue fighting and more important to be able to limp back to base for repairs. Although being able to fight would be useful as a defensive measure as you return to base (while the enemy is shooting at you.
The A10 is a good example of designed in redundancy survivability.
All those are there as the 3rd backup. Manual traverse and elevation. 105-D “choke” sight (optics) slaved to the main gun. Manual blaster to fire the gun. Its always been there and always will be.