The original Apple LaserWriter did offer ImageWriter emulation, when connected via it's serial port, and later Apple shipped a Postscript based ImageWriter emulator for localtalk connected LaserWriters with GS-OS for the Apple IIgs.
Have you gotten this to work? I've tried a few times with my LaseWriter, and while the emulation loads it does not actually print ImageWriter data.
-J
I don't have a LaserWriter now, but back in the 1980's I did use the LaserWriter emulation mode and it worked, but I realize it was the built-in Diablo 630 emulation and not a ImageWriter emulation.
AFAIK, the PS ImageWriter download that was included with GSOS only worked over LocalTalk, and would not be much help for LOS..
Rick