The virtual font system is an ingenious system of font substitution
that would allow DVIview users to use the normal Acorn fonts in their
documents and to replace missing TEX fonts with other fonts (either TEX or
outlines). Implementing virtual fonts in DVIview doesn't look particularly
hard, the problem, however, is creating the virtual font files (vf) and
TEX font metrics (tfm) files for the RISC OS fonts. These can be created
by hand in the form of human-readable vp files, which can be converted
to and from vf and tfm files using the vftovp and vptovf
programs, which are supplied in Robin Watts' TEX distribution.
I suspect that the vf and vp files could be partly (and maybe fully) created
automatically from the RISC OS IntMetrics files but this would require
someone to write the conversion program.
Another option is to try to find the vf and tfm files for the equivalent
postscript fonts (at least the Courier, Helvetica and Times families) and
modify these.
If someone has the relevant vf and tfm files or is prepared to attempt a
conversion program (I can provide details of all the relevant file formats)
then let me know.