Dave , ever thought about going the other way?
I'd keep rest periods to a minium, but just work on doing more burpees/box jumps per miniute!!
I understand your point that obviously there are different levels of fitness, but if your not going all out for the miniute its not hiit, and your not going to benifit as much.
Id be inclined (and its how i train my boxers) to do as much as you can IN your set time with minimal rest , and then try and do more next time.