But I dropped this idea because I wanted to extend the printing possibilities beyond the limits of physical printers. And because I don't know anybody who would need this feature.
For example, Epson LQ printers don't offer the possibility to print in Landscape mode (www.missico.com/personal/support/epson_escape_codes.htm).
I also thought to emulate HP instead of Epson (they have a Landscape mode), but HPLG is quite difficult to parse because the syntax is more complex.
Alternative products who emulate real printers: DOSPrint 2.5.4, DOS printer emulator, DOSPrinter