[linmer]

Yeah, but the difficulty isn't in rendering the fonts, it's for the font creator. So once the font is ready with all the combinations it rendering and using a Nastaliq font doesn't differ with rendering a Naskh. Nastaliq fonts are available in Persian, not sure if true for other languages, but it's just more complexity on making the font. For using a ready font the only thing needed is permission to change the font.

[bradrn]

Yep, that’s what I meant; thanks for clarifying the point.

(Though that said, a sibling post linked this interesting talk on limitations in OpenType itself: https://www.tiro.com/John/TypeCon2014_Hudson_DECK.pdf)