I daydream about this subject at least once a week. My wife pretty much gave me the green light to go to JPop's school if the $$$ and time vested, was reasonable. I would love to contribute my skills to non-licensed themes but, even more than that- I would really love to give lesser cult movies/themes their day in the sun! Since pinball is now considered (to me) a subculture, why not cater to pleasing the few with some offbeat titles that the veterans wouldn't touch. I know it's not the smartest business decision, but if I had the scratch, know-how (and time) to build 10-20 machines to completion and they sold- well I'd be a happy camper for sure! Pinball to me is not about making tons of cash, it's about making a kick-ass pinball machine that is amazing to play.
Again, this is all a daydream for me so don't put too much stock into it... Yet!
If JPop's school does work out and a twilight freelance pin-career is feasible without eating ramen daily, then consider me your guy!