Mike Thackwall always struck me as someone who should have made it in F1. He had a few stabs at it in uncompetitive machinery, had a couple of races with Penske in CART, then won races in F3000 before quitting the sport. I'm not sure if it was a case of not getting the breaks, or not wanting it enough, but he had the talent to do more than his record shows.

Stephen South was another who seemed destined to do well. He could have been in the Toleman team that dominated F2 with Henton & Warwick, tested (IIRC) for Lotus at the same time as Mansell, but made just one DNQ appearance for McLaren at Long Beach in 1980. A serious accident in Can-Am ended his career.