I'm not a LilyPond expert, so I'll pass this on to the list, but I
would expect it to be fairly simple to change the clef font. A
question of my own: can users build new fonts from old within
LilyPond? It'd be cool to let users create, say, a clef font based on
the usual clef font but substituting their preferred version of the F
clef from another font.