This is good stuff. I've tried to advocate a naming convention that would be appropriate to this. I would suggest calling this texnansi-osfsc.enc, as baseencoding-variant.enc. This is so a modified encoding can "masquerade" as the base encoding within ConTeXt.
Given this encoding with my suggested name, you could therefore run texfont as following: texfont --encoding=texnansi --variant=osfsc --[other options] That is by far the most elegant solution indeed! I have renamed my encoding file.
Variants that select rarer features that Old Style Figures and Small Caps may need to be given font-specific names, as rare glyph names tend to vary wildly between fonts.
Sadly, you are absolutely right about this. And it's not only rare glyphs that get wildly different names. There was some rumor on the TeX on OS X list that people couldn't get the beautiful HoeflerText font to work with TeX; it turned out that this was true for newer versions of the font only. I looked into it, and it turns out that Apple (?) has given new names even to quite "normal" characters - eacute becomes e_acute etc. So if you want to produce a tfm for that font, you have to invent a specific encoding vector. Once you know how this works, it's easy enough, but really annoying. So, the "variant" scheme in texfont is at least a convenient way to cope with this mess. Best Thomas