Hey, so how restricted to realism are we? Like I can see two psychic characters and laser weaponry, so obviously there are some sci fi elements at play. 
Because I had an idea inspired by [url=https://www.reddit.com/r/UnearthedArcana/comments/r3izd1/the_incarnate_v20_the_martial_kaiju_class_returns/?utm_source=share&utm_medium=ios_app&utm_name=iossmf]this[/url] D&D homebrew. 
So here’s my pitch. 
A soldier that has been experimented on with Kaiju biological material. Probably Stem Cells from a fallen Kaiju that was pregnant at the time of its defeat. He would inherit a few abilities from Kaiju, but most notably, he would become a living nuclear reactor. He would function as the brain and power specs for a new prototype mech to combat Kaiju. 
Ad he biologically functions as a nuclear reactor, producing mass amounts of energy, he solves the issue of finding a suitable, sustainable energy source for the project. 
Thoughts?