Here are some thoughts:
(1) For IMAX1 I substituted IMAX3 (b.c in the rotation for that week you won't be doing it until the end of the week.
(2) For Circuit Max, I would substitute either the premix on Step, Jump, and Pump that says "Step and Weights"--that is a pretty comparable workout, b/c you are taking out the hi/lo portion of S,J, &P; otherwise you could do Cardio& Weights instead.
(3) For the 2 high-step workouts--hmmmmm, that's a toughie....I am assuming you don't have IMAX Extreme--if you do, I would do the workout on that tape that includes Highstep Challenge as a substitute for HSTA and ASC. Otherwise--do you have the Terminator DVD? I think Gauntlet would be a good substitute.
(4) For Abhits, that's easy--any of Coremax is so awesome (that's what I substitued) or any of the Ab sections from one of the Cross Train Express Series.
(5) Finally, for running--I would substitue either a Kick, Punch, and Crunch (if that's not called for the next day!) or a good steady intense step tape like Step Blast, or MIC (but I would probably leave out the step portion of it, unless you are feeling extra energetic!)
Good Luck to you--I am starting week 3 of the rotation tomorrow--so far, I am LOVING it, but the homemade workout for tomorrow has me a little frightened!!!
Melissa