[fhars]

Specifying the rules for German Fraktur as executable code will be fun, as it uses the short s at the end of syllables, not words. So it is "Häschen" and "Häſcher"...

[dpkendal]

Unicode has things for this: https://en.wikipedia.org/wiki/Zero-width_non-joiner

And customization is done declaratively, not imperatively.