Nobody ever said making a custom couldn't be easy. Simple, even.
A lot of customizers are still eschewing the 4" Marvel Universe figures, opting instead to use their time to fill holes in the 6" Marvel Legends line. However, this is a custom that can be made by anyone with thumbs, and it takes about 30 seconds to do, so perhaps this simple start will put more attention on the little guys.
Professor X can be made by combining three of Mattel's subpar James Cameron's Avatar toys: the wheelchair, obviously, comes from Jake Sully; the body is Parker Selfridge; and the head was originally Corporal Lyle Wainfleet. All you have to do is pop the heads off the bodies and switch them - the plastic is soft enough that you don't even need to boil them first! Just open the toys, pull the heads off the balljoints, and pop them on the other torso. There's no sculpting, no cutting, no repainting... creating Professor X is exceedingly simple, and since the Avatar toys have been showing up at discount closeout stores, it's not terribly expensive, either. Granted, Mattel's figures are dwarfishly small next to Hasbro's, but since Charlie's sitting down, you'll never notice.
Repaint the wheelchair or leave it yellow? Tell us on our message board, the Loafing Lounge.