I think I suggested this a year or maybe two years ago but, I figured I'd try pitching the idea again.
It always baffled me that players would attempt to preserve AGTs and Obelisks ever after their Power Plant was destroyed. I know the tower defense exists after the fact because its still a base structure but, it really has no value once the power is lost. I always thought the 'Weapons Offline' message could have had more to it which brings me to my idea...
What if the AGTs and Obelisks could be reactivated to a less efficient capacity as long as 1 Engineer (or 2 infantry repair guns) repairs the MCT?
Similar to how 2 Tesla Troopers could power offline Tesla Coils in Red Alert 2.
For balancing reasons, the 're-activated' tower shouldn't regain its full efficiency but, maybe have a 50% slower reaction time when targeting enemies.
I'll elaborate on the lower level of efficiency:
I'm also not saying that the towers should ever become capable of overcharging (like Red Alert 2) because that would be OP.
The intention of this proposal is to give offline defense towers use after their power supply is cut off.
When it comes to in-game practicality, it would temporarily reinstate the tower but, at the price of having 1 or 2 (if infantry repair guns are being used) players manning the MCT instead of helping on the battlefield. So, if there's no one charging that MCT, they're as just useless piles of concrete for you to change your loadout inside of.
In a way, it could serve as a last ditch effort to fend off the inevitable final rush without relying almost entirely on grenadiers and flamethrowers.