I had a chance to use the machine a few more times. It's not that bad to clean out as I first thought. As long as a water hose is available to do a quick interior rinse of the tank, then there shouldn't be any issues. There are quite a few contours inside the main tank, so wiping that down without a hose-rinse makes it tedious... and fiddling with the non-original pre-filter setup (explained below) added extra time.
I decided not to take photos of the filter assembly since it is not the original design. Someone modified it to keep a different center stainless mesh filter in place (which had a broken off edge on one of the sealing surfaces, allowing semi-unfiltered water in. Which is probably a good reason why the hand tool nozzle is plugged. Around the stainless filter, they put a stainless wire cage, with a disposable cloth pre-filter seen in the above photos.
It took awhile for me to find a picture of the interior in the original setup. This is how the right filter, which can be quickly replaced and rinsed looks.
In either case, I'm growing more fond of the machine. I likely don't have to worry about any warranties at this point, so the modifications to the machine won't end here
I'm going to sandblast the outside aluminum and repaint the machine. Replace some of the stripped, mismatched panel screws with new stainless ones and make it looks fresh again. I did a quick visual inspection inside, and it seems like there should be enough room to mount a second 3-stage 5.7" vac motor, after I relocate one of the tank vacuum exhaust lines. Does anyone know how dual motors are normally connected? With both intakes joining with a Y-connector or something?
The regulator is due for a rebuild kit at 500 hours, but I may instead replace it with a 0-600 psi pumptec regulator for some performance enhancement. If that modification works well, later on I may try to figure out a on-demand water heater setup, which would likely have to be mounted at the back of the machine for space reasons.