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Then simply restrict yourself from putting too much non-peasants on it. Sure, you can min-max the hell out of it, but the branches are more or less your own choice in playstyle and a bit of roleplay. Might as well say that "Reject the Power" is redundant, because picking any codex is better from powergaming perspectivie.
In my opinion if something is OP, but one could easly either not use it, or restrict himself to use it fairly, then it isn't a problem.
And there really doesn't exist a half-decent reason why gals (or any other race, or just males) couldn't use Harvester. Civilian Agrocultural machine shouldn't be much different in operating than aircar, airbus, or airvan, which gals operate with no problem.
The "principles of revolution" argument also doesn't hold, because of a quote from "Peasant Revolution!" after research sreen:
" ...Whatever number of Gals or assorted adventurers you can raise for your cause, it's not big. Big picture is the peasants. They're everywhere, they're the backbone of Earth's society. After all, they provide food. If only they weren't so passive...! ...But with their bravest girls as the vanguard, and your Gals as the tip of the spear, they can be roused from this slumber... and the world will never be the same! You have communicated your grand ideas to a council of village elders. Most of them said you're insane, but you did manage to rouse a small cadre of idealists. It is enough for now; in time, you believe truly, it'll snowball into an avalanche!..."
Uber Gals are considered a part of this revolution. One could make argument against Lokk'Naars, but what those little goblin girls are any different than your common peasants in terms of joining the revolution? Especially when taking gameplay into consideration, where they are surely weaker on average than gals. And what is the problem with armored cars being transported there?