I got the project far enough to come up with a rough floorplan:
It took quite a bit of fiddling with combining loose parts into resistor and capacitor arrays, reducing resistors to 0402 size and throwing out optional parts, but I think I have enough confidence to say now that this might be possible!
The design will be isolated, but things are just too tight to be able to keep recommended clearances and make any claims about the isolation voltage. I will have to go to smaller via sizes and trace widths and clearances than I usually do, but that's alright. Most board houses nowadays have no issue with 4 mil traces/spacing and 0.2 mm via drills.