This evening, I actually made some progress on the crawlspace under the house. I went in there with no illusions, and lots of equipment, including goggles, rubber gloves, safety shoes, and a P100-rated half-mask respirator.
In a bit more than an hour and a half, I mucked out four garbage bags' worth of sundry unpleasant substances ranging from wood-chip insulation to nuggets of *bleah* fossilized cat poop.
I also took a hacksaw to some old ABS drainpipes and vent pipes, and capped them off. This clears the way for finally dismantling the unused shower in the mud porch bathroom, and removing the old closet flange. Once the floor has been properly supported from below, the newly-cleared area will become the kitchen pantry, and a new toilet and sink will be installed in a much, much smaller bathroom.
Probably by a contractor. There is a certain charm to doing all of one's own renovations, but I'd rather have a professional plumber do the roughing-in.
Because I really want to have that bathroom operational for this year's Jól party.