I think I'm getting close with epson2ps... It does the right thing with a flat ascii file.
Would've been a lot easier if unixlib included open() but I guess that's too much to ask of a UNIX compatibility library. :-/
After running the result of epson2ps through ps2ps I get a file RISC OS gview can display! Woot! (ghostview just exits)
epson2ps and ps2eps, gview can display the file, ghostview renders all the output onto *one* page.
epson2ps and ps2pdf, gview, ghostview, and !pdf can display the results properly!
(ps2ps, ps2eps, and ps2pdf are all scripts calling ghostscript with various options)