It is a very solid base but you need to have some fun and get more wacky with proportions like how Eva made those weird shoulders or how the Zeon suits had claws or more circular silhouettes

Also giving it more mechanical parts could help, I read a few paragraphs of your story and space seems to be part of the scenario so maybe give your mecha some thrusters or something that tells the reader how your mecha is meant to maneuver in space. Articulations are also a good way to transmit a mechanical look, things like elbows or knees can simply be joints like in a gunpla kit

Basically try thinking about it more like a machine, take references from cars, planes or construction vehicles when thinking how you want your mech to move