Unfortunately, I find it hard to let go of an idea and you really put the negative training bug in my mind. I just completed my second set now, and this is what I think worked.
One handed row - not really working, hard to isolate the back.
Leg curl - I already trained with this, as I find completing the curl difficult so use my hands on the wire to help then slowly lower. Strength has increased since training to failure.
Leg Extension - getting close to maxing the weight on the rods, don’t like using 1 leg exercise. Instead, when lowering, I push down the bar on the extension device. Could barely walk after this.
Bench press - one hand helps lift the other hand with overload of ~ 40 % my usual. Think it works well. Just about smashed my self in the mouth when the muscle failed. No real burn after.
Tricep Press - similar to bench press. My arms were killing me on this.
Shoulder rotation single arm - not sure I have the right form on this.
Bicep concentration curl - felt it was good.
My regular routine is lat pull, standing tricep, leg curl and extensions, bench press, ab crunch, seated shoulder press, bicep curl. Do this routine first then negative routine.
So, in the end, it can be done. Worked well on bicep, tricep, pecs. My legs I like as well, Back and shoulder were disappointing. There is probably too much rest time as you recommend completing the positive and negative routine in one exercise instead of splitting them apart.
This came about after trying the 30 -30-30 routine. Very difficult to do without a training partner which defeats the purpose of the Bowflex. I did read over the 30-10-30 and this makes way more sense as a routine for me. This will avoid the long rest between sets. My muscles were only slightly sore adding the negative training, so I don’t think it is as effective as I hoped.