So it feels like to generate strong punching power you'd need starting strength, high RFD, and good limit strength. General exercise + Plyometrics, Westside , vand dyke style training or triphasic training, contrast should work very very well for that. But I read an interesting thing by Waterbury and always wondered if he was right. http://chadwaterbury.com/should-you-bench-press/
(An immediate counter example would be Shane Carwin if I'm not mistaken, who mostly bench presses).
He says that since you retract your scapula when benching, it neglects the serratus anterior and the transfer/efficiency of transfer to the mechanics of a punch are subpar.
Also wondering about overhead pressing, eventually very explosive, as a carry over towards punching, since it's a rather different plane of movement.