How does this idea for a homebrew Mech world

[LoA]

So I am still on the hunt for a Mech RPG System that Appeals to me, and I came across this Reddit post:

A bit different to the other answers, but I had a half-finished mecha homebrew.
For the pilots, use d20 modern characters.
For the mechs, use 4e d&d characters.
Have them on two different scales: Mech scale and Human scale. Human scale entities have weakness vs mech weapons, and mechs have resistance vs human weapons (unless they are specially designed mech-killers).
Using this system, you have characters running around in things like 'Paladin Class' or 'Assassin Class' mechs. Different sets of powers represent different system/weapon load-outs.
My rationale behind this easy homebrew is that I wanted a system that allowed for customisation, without players having to worry about cooling units, gun mounts, chassis limitations, etc.

Link
I actually really like this idea. At least in it's spirit. However I don't use 4e like the pleb I am. Do you think using FATE for characters and PF for Mechs would work in it's place?

[Steerpike]

That's a pretty oddball combination, and it feels like it would take a ton of work to get the Pathfinder characters to feel like mechs.

That said, it sounds like to the reddit user, that's part of the point, so maybe I'm crazy, but personally if I were playing a mech game I'd really want to nerd out over "cooling units, gun mounts, and chassis limitations" - surely designing a mech is a huge part of the fun?

Have you heard of Mechnoir? I think you also need Technoir to run it but even together, they're pretty cheap. It's like a relatively rules-light mech setting.