Given that many heresies in HIP already have a sort of "reformation" option already available, and that those sorts of things were put in well before customized reformation was a thing, I can see the potential. I'll have to look at how they do it to see whether it's too hacky to be viable in HIP, but if not, then there's at least potential to try and meld that mechanic with the reformation systems that we already have in place (for, say, Bogomilism).
EDIT: In reading more on that mod, I realize now that it is just a simple "reformable heresies" mod and not something involving abusing the new pagan reformation mechanics for heresies, which was what I was interested in. In that case, most of the features they added are already, in a more realistic form, in HIP. Every heresy can be "schismed" out of their parent religion, for instance. Several can have a religious head established, with differing systems depending on the particular heresy as to who that religious head is (secular ruler, elected like the Pope, elected like the Ecumenical Patriarch).
In short, we already effectively have all of what that mod offers.