Actually, #Plan9 4e has a program for serving the old 2e/3e protocol (9P1). And so maybe 2e has a program for serving the old 1e protocol (which I call 9P0)?
So if I can't get the 1e stand-alone PC version working, maybe I get 4e serving PXE+9P1 to boot 2e, and then I get that serving 9P0 to boot 1e?
Keeping the boot quirks of multiple versions of Plan9 straight in my head at once doesn't seem fun tho.