So I did take the risk and swapped out the battery without doing the logic-board + speaker removal.
Before applying the acetone I put tape on the exposed sides of the speaker-enclosures as best I could - I wrapped the tape, sticky side out, around a card, slid it into the gap, and pressed it onto the speakers. And when applying the acetone, I squirted it as gently as possible onto the side of the battery and let it run down the side, which seemed to help avoid getting too much on the speakers.
The speaker’s plastic turned white in the spots where the acetone touched it, but it looked like surface damage only. Otherwise it was a nice and smooth procedure.
Your milage may vary, obviously.
Do we remove the logic board purely to get the speaker enclosures out and away from the acetone? Or does it physically block getting the batteries out? Ie. if I wanted to risk the damage to the speakers, could I jump straight to step 34?
Obviously I don’t want to melt the speakers, but I’m kinda weighing that risk against losing a screw or breaking a connector…