I totally hear your frustration. I know this is against dogma, but I've added timed rest into my training. I use a rest period based on the time under tension. So for RC/PE6 this is 90 seconds. While the 90s is going on I do the mobility. This ends up giving me about 30-40 seconds between the mobility and the next set. It was driving me crazy though that the rest wasn't controlled. Now, my set times are consistent and I can further compare one training session to the next. Also I can move that rest up or down comparatively as well.
I'm also a larger person at 220lbs and 6'2".