To the original post, the easiest way to cut white flexi pipe is a hacksaw, not a sawzall. Also the crescent "soft metal" cutter head on your multicrafter tool works pretty well, but the hacksaw remains easier, and possibly quicker. I can't speak to more rubbery hose.
For catching goo, I live in Canada, and the "wait for the freeze" is a great strategy. I removed my holding tank
last winter that way, having to tilt and twist the tank out of place with the pipes taken off. Worked a treat with the the contents frozen into a poopsicle such that there was so much as a drop lost. That having been said, at -20C it takes a while to soften the flexi pipes with a heat gun for removal from the barbed fittings. When I've removed a section of pipe in more moderate seasons, instead of spray foam I have stuffed the ends of the pipe with paper towel - hard. That works for the upper end, but if you have to take the end off the toilet, you're pooched.
Late this past season I removed quite a bit of the longish snake of white flexi pipe from inside and under cabinets and such, and replaced it with PVC. It's a much shorter direct run on the toilet to tank intake now. My thinking was twofold, the PVC is much less permeable, and the short run (maybe 18" vs 5 feet) allows me to use much less water when flushing to clear the pipes well. With only a 15 gal holding tank
, this is advantageous to me. On the pumpout side, there is now no low point of flexi pipe to accumulate sewage. I hope/trust that the PVC will remain non-stinky at that low point for years to come.