How are you going to address the fact that the same letter (even in the Latin alphabet) can have wildly different outlines? Just look at the character "a": some are circular, others have the "hook" over it. Or the "&": some are more like a continuous stroke, others spell "et".
More parameters -- enumerated ones rather than real-valued ones.
The "two-story" "a" is default, but set a bit to choose the single-story version. Similarly with a lowercase "g" and so on.
(And of course plenty of existing fonts already give variants for these kinds of things too -- so the user could even still choose an alternate one, even if the font designer never designed it!)
