I have a head canon that Brain Drain was a bit of a loser when he was human but had great latent psychic potential. A slacker, used his talents for cheap parlor tricks or to cheat a poker, but couldn't really push his abilities to make him dangerous. After the accident, he underwent a personality shift and strived to be this grandiose, methodical evil genius. As a result he became immensely vain. He could have gained a stylized and simple body, but instead, he has what appears to by a rather muscular physique underneath his fancy coat.
Here's where the weirdness comes in. He obviously doesn't see himself as evil, but as the dark hero the world needs to take the fight to all the cosmic horrors..it's just that, he sees himself above morals, and things like...pity. When crafting Painwheel, he applied that twisted concept to her. He, in his own way cares for her and has crafted her into his ideal daughter-like figure. A cold, powerful and visually arresting figure. By making her perfect he also made sure that she couldn't remove her mask. Why? Why suture and staple a mask to her. Faces. Brain Drain hates faces.
In producing his perfect child, he needed to get rid of such a feature without "hurting or disfiguring her" Sure the pronounced veins and gait are unfortunate, but they are necessary evils for Skullgirl slaying and experimentation. Why does he hate faces? In his grand vanity, he realized, he couldn't find a perfect face. The unemotional bits of metal and plastics served their purpose, but then, Brain Drain started becoming unnerved that he couldn't laugh, couldn't sneer, couldn't grin at his genius. It started as an annoyance, but then became, a point of obsessing. He tried other casings and renovations, but...nothing felt right. Sure they were more menacing than his original...human face, but still. It felt wrong somehow, artificial. It mocked him, in all his greatness, with all his resources, he could make other bodies, other faces...but nothing felt right. Nothing felt like it was...him. IF he could not have a face, why should his potential heir, his daughter, his grand creation have such a strange feature....why indeed?
I er...ahem, may have looked too deep into speculating his character when I voiced him...I...I think I know how he thinks...I'm gonna go lie down and hope I don't wake up a Brain in a cybernetic body...