What's a Minstral?
A medieval singer or musician or entertainer, usually remembered as one who sang or recited lyric or heroic poetry to a musical accompaniment for the nobility, it can however be applied to most forms of live entertainers.
What's a Minstral?
I kow I'll never live this down........ Shiro
Sapphire, because Gren will conquer her!
Again, why would his aura not be even distributed if he has a specialized organ made precisely to distribute aura through his body? If his aura isn't evenly distributed through his body, then he couldn't move it in the first place. Aura is effectively his blood, and it's the reason why EMP's are even effective against him since they fry the circuits his aura can flow through. Gren's power source is suppose to be able to allow him to distribute aura throughout his body evenly, both for the purpose of making it function as well as protecting him. The idea that it's not active all the time or unevenly distributed means that he's either turned off, or a part of his body isn't working i.e. is broken.
Plus a clean power source, even an electric one, would require even more advanced tech then simply being powered by aura, which we can at least assume doesn't have any sort of byproduct. Sure he does need biofuel for his thrusters and his extra electronic bits like his built in phone and camera uses electricity, but those could be safely disabled/their power source removed without affecting Gren's ability to function. At worse he looses mobility, communication, and perhaps the ability to make his helmet cover his face at will. Otherwise we'll end up back to that discussion with the fusion core since apparently he's now running off some sort of engine or fuel that is small enough to fit inside his body but has a power output strong enough to power him indefinitely, especially considering the sort of feats of strength and endurance he preforms.
That's assuming that just because Gren lacks most of his original body, his aura is suppose to be weaker. This isn't Star Wars where cybernetics are inherently conflicting with mechanical parts or even armor. Besides that most of his aura already goes into making the machine work anyways, and that isn't limited to just allowing him to move. It effectively pumps his aura throughout his entire body like a mechanical heart, precisely so he doesn't need to constantly focus on pumping his spiritual blood all the time. With the benefit of doing what aura is suppose to do anyways, like protecting its person.
Gren's aura is constantly active for both protecting him and allowing him to live much like Sapphire is constantly breathing. Because as discussed before, Gren's aura is what is powering his body (since we also nixed the idea of alternative energies like dust or fusion cores). We also had mentioned that while EMPs are effective against Gren, it's not instantly lethal, only that it shuts down a vast majority of his functions beyond what's keeping him alive. I.e. Moving at all.
The idea that he's constantly struggling to make his heart use his aura to just keep him alive is frankly kinda ridiculous,
...not to mention making him much more of a liability If he can't rely on his aura to serve a basic function everyone can do.
If you want to nerf him that badly, I'm willing to satisfy that desire by limiting his semblance instead, shortening its range and adding more caveats to avoid being affected by it.
I just had the best god damned waffles of my life.