Good points and these are negatives and challenges. The heat that I have is an external heater by esteam and it heats in 1 min. What I do is as soon as I turn on the machine and the heater the water is usually warm from the hot tap water so I start cleaning the non traffic areas like the wall sides or maybe there was a bed there which was moved for the cleaning and by the time I am done with these areas I have full heat 140-150F for the filthy area.And others would redo your portable to eliminate the heat and add more suction.
The low psi can be overcome by larger jets.
The heat will slow you down if you actually want to use it because you will be waiting for the water to get hotter.
However this wait can be taken up with 3 or 4 dry strokes per wet stroke to alleviate some of the issue of low suction..
I think Franks reliance on agitation and maximum suction might go better.
Extra Dry passes of minimum of 3 will make things go slower.
I got about 230 psi so it is not too bad but still I prefer minimum 350psi which flushes away the dirt better with good 3 corded extraction system....