It might be a bit heavy, but shouldn't be too uncomfortable, if you mount it on a frame of some sort, but what about having an L5 heater on your back, with water supply and gas bottle and circulate hot water while cleaning?
Can someone come up with a way, maybe using a trolley system (?) to heat the wfp water, and before it gets to the glass, runs through a special immersion heated suit and gloves to keep you warm?
The suit might look a bit like this without the mask:
