I suppose the next evolution for the m0n0wall CD version would be to include an installer - ala pfsense.
But it would seem to me that it's probably possible to use just about any available Linux Live CD to download a copy of m0n0wall to RAM disk and use dd to install it to HD or Flash.
physdiskwrite is a Windows/DOS type application and that forces unnecessary requirements onto things.
You mention DSL; that's already covered here:
http://m0n0.ch/wall/installation_generic_dsl.phpIf you don't have a CD-ROM drive but only a floppy, that's here:
http://m0n0.ch/wall/installation_generic_tomsrtbt.txt