Wario being an electrician feels like a natural fit to Mario's similar-yet-different plumber. Of course, most of the electric work we've seen him do is... done to him, through lightning strikes and electrocution, but not many electricians have the skills to survive such high voltage. He's clearly qualified at least!
I never really considered what it'd be like with Wario working for others since he's always in it for himself and with him as CEO it's the opposite and people work for him, but I agree that some sort of tradesman would be a good match with Mario
I think it'd be cool if he was a mechanic! The Wario Car is slick as hell as well as his motorcycle and I like to think he's really proud of them and keeps them in great shape