As someone who often prefers alternating strength and cardio days, I'd also like to have some more cardio-only workouts, similar in feel to the earlier workouts like those on the Classics and Cardio Hits DVD's: long step segments. interesting choreo, but nothing too fancy to take away from the intensity of the workout (and not so many pivots, which aren't so friendly on the knees).
One idea would be a hi/low max (like the Imaxes, but mixing low-impact intervals with higher-impact intervals, maybe 10 intervals in all: 3 low impact, 4 higher impact, then low, high, low).
I'd also like to see an all-cardio vertical step workout (as a change of pace, and for some new choreo possibilities), or perhaps a workout with some segments using the step horizontally, and others using the step vertically.