Well, you can start off by creating a basic recolor of Silver Men / Dummies and some weapons mod, then tweaking it bit by bit, improving the detail and making weapons feel more unique, eventually releasing it when it feels satisfying enough.

Isn't there a lot of "gib" sprite drawing, and coding?

i thought of this idea to and posted it on the "what mods would you like to see discussion" as an idea
but i think what teleno says is just about correct but personaly i think reskinning imperatus units would be a better way to do this because of the rugged and slightly damaged fell they have

*feel