Vitali Klitschko, who also had a career as a kickboxer. He changed his training due to injuries (a lot of swimming) and changed his style and fought more and more unorthodox.
Turpin with weight training. Cribb with Barclay Allardice's workouts (which were a terrible idea, by the way.) I think Ray Mancini employed sport psychologist James Loehr to improve his mental toughness in the ring. Holyfield with Fred Hatfield's training regimens. Spinks with Mackie Shilstone. Jeffries with Ernest Roeber's wrestling training for clinches.
Oh, and Lou Nova did yoga in the 1930s and 1940s, of the mystical variety. Not sure whether that counts as forward thinking, but it was certainly unconventional.
Very open minded was „Two Ton“ Tony Galento (taken with a pinch of salt) who also fought against the yoga trained Lou Nova. About his training and nutrition: https://en.wikipedia.org/wiki/Tony_Galento He also had some questionable promotion methods like fighting a kangaroo, a bear or wrestling an octopus.
