The series takes place on The MOON. Robots aren't commonplace in war at the beginning (although powered armor is), but an advancement in artificial muscle technology is suddenly makes it possible. Only, robots have kinda slow reaction speeds at first and there has yet to be a breakthrough control system to make mecha really shine. AI aren't trusted, remote control suffers lag issues (although you don't lose the pilot, so they are the Disposable Goons of the show), and most machines that put a man inside are slower, more "western" style mecha that only crazy people step into.
The breakthrough is when a brilliant engineer realizes that the best control scheme is the human body itself. Our hero is a quadruple amputee with heavy cybernetics that connect prosthetics to his nervous system and who lost most of his limbs as a child, and the engineer makes him a custom bot that basically works like a giant set of prosthetics. Our hero is fast, experienced with moving, knows kung fu, and is all gung ho to fight the GREAT MARTIAN REBELLION. He's not a guy in
a mecha, he IS the mecha!
At first, he's an absolute terror on the battlefield, but soon others follow and he's no longer the only amputee with a mecha. Now the military is recruiting anyone with cybernetic replacements they can get their hands on, especially veterans from the infantry. The enemy soon learns the trick as well, and now the show shifts focus from the GLORIOUS WAR story to the morality play. Our hero starts seeing people with all sorts of messed up backgrounds being either recruited or even FORCED to pilot because they are natural ACES on the battlefield. You got the veteran who is guilt tripped into continuing to fight for his country while secretly struggling with PTSD, you have the enemy soldier who wasn't injured but surgically altered
to be an ace, you have the girl whose body is paralyzed yet they think that if they hook her brain-link directly into a computer they will have an even greater advancement that will make the rest of them obsolete. Oh, and maybe a conspiracy to take all these innovations and create a true AI controlled mecha-- and have to "invent" a person with a false identity to fool everyone as well. And all our hero is left thinking is, my god, what are we all doing?!
They're winning the war, but at what cost!!!1?
Throw in a role model for the hero who fights in the air instead of the ground so that we can eventually have that talk about how distant the fighting can seem for fighter aces VS mecha aces, and we can make it as topical or as timeless as you feel is necessary. Bonus points, this premise gives you an excuse to make every single hero mech unique and customized as its basically less a standardized vehicle and more an extension of the character's bodies in almost a literal sense-- you can't just take one pilot and put someone else in their mech because the mech adapts to the pilot and not the other way around. Heck, it even gives you an excuse to use that old anime trope where the characters call out their attacks, as they would need voice controls to activate weapons and stuff that isn't a part of their phantom limbs.
Inspired by such real life research as this