Excellent!
I think that Stuart body really lends itself for being "Meched".
Personally I would go for thin "Manipulator Arms" like the ones on some of the GearKrieg stuff. You should be able to fashion some out of plastic rod. Like WK said it's difficult to tell without it being painted.
The legs are a little skinny and would make any easy weak spot to target by the enemy. Some armour plate would look good and would bulk them up a little.
I agree about the robo-gear legs, they are really big. I think looking at the mini next to it, those sentinel legs are spot on for height.
Look forward to seeing this one painted!
Regards
PM