I'm not sure if this is going to make much sense, but well…
The threads on Arabic همزة in the Arabic forum made me think of the situation of Persian همزه… I've seen many, many examples of it being used with ی in the form of ئ, as in امریکائی and کانادائی, or even in transcriptions of (foreign) names, such as رافائل, and I'm (probably) fine with that. But I was wondering—is it ever used on its own (ء) or combined with و in the form of ؤ, or even combined with ا as أ or إ? And, in case it is, is it used only for borrowings such as those from Arabic, or also in Persian native words? Which would be the rules behind those for Persian?
By the way, I'm comfortable with its combination with mute ه in اضافه constructions (such as [r]خانهٔ مریم[/r]), so that's not a problem.