On the hiring of anyone with the appellation "Mad": Just don't.

While there may well be uses for the insane in some (very) specialized organizations, I have yet to discover one in my own. This includes the criminally insane. Essentially, the point to be made here is when you hire/intimidate/blackmail someone into performing a task for you, what you want is results - predictable, calculable results that you can plug into your grand scheme. What you get, when hiring unhinged loons (and they all are, your Evil geniuses, Mad Scientists, Crazed Sorcerers et. al.) is chaos.

And anyway, why would you want to hire a mad scientist when there are so very many sane scientists out there willing to invent and improve upon the most heinous technology, and for nothing more than a decent wage and modest benefits? Sure, the mad scientist or crazed magician may be willing to work for free, just to prove his theory correct. But you have to remember two things here:

1) By and large, you get what you pay for, and
2) he or she is not working for you , or to advance your interests, but to prove their mad theory correct. He/she is in the grip of an obsession. And he/she is bug-f*ck crazy.

You do the math. Cutting corners is a bad idea.

A final thought: If you simply can't help yourself and decide to take a chance on the Mad Alchemist of Prrng or whomever, make sure you give him or her a research facility, far, far away from anywhere you might mind seeing turned into slag. It also wouldn't hurt to name the facility after a dead relative of your worst enemy, e.g. "The King Gustus Memorial Institute for the Advancement of Magics" or the like. That way, when things inevitably go spectacularly wrong, public backlash is channeled ina useful direction.