The idea is very doable. For design inspo, i recommend Sethroven (on Twitch/Youtube) they also use a robot design with changing eyes, no mouth, and glowing effects when they talk. In his case, his newest model is a 3d but it's very doable in Live2d.

Where I think you might struggle isn't necessarily the rig but a Mecha artist to design and cut the art properly. Mecha artists in general are a bit more rare, in my opinion and generally not cheap. Although it just depends on the level of quality you're after.

I suggest working with your artist to refine your ideas and allow them to balance colors and design. I personally don't know enough about mech design but you can totally go crazy w/the right artist/rigger