I think Selectfont is great -- thank you, Wolfgang, for your work.
However, I miss the features to define and use additional typeface
styles and alternatives.
Not everything fits in the predefined scheme of rm, ss, tt, hw, cg and
mm, so it would be nice to have the possibility to define additional
typeface styles. (I'm thinking for example about blackletter here.)
It would also be nice if one could access arbitrary typeface
alternatives, however the typeface creator has named them (e.g.
something like semicondensed-ultrabold). At the moment, I think, it is
only possible to map a few alternatives to the predefined switches.