Does this belong in the EU4 section or CK2 section? The converter is a CK2 DLC...
But that aside, I see two easy outs even if the converter 100% hates Hellenism (which it seems like PDS is regretting putting in, since we keep using it for unintended purposes

):
1) Mod Hellenism to allow it to reform. Easy peasy.
2) Mod the conversion mod to put Hellenism into a not-shamanism religion. Also easy.
edit:
In any case, the converter can be modded to port it easily according to Pdox. I'm certainly doing it, my great Hellenic Roman Empire would look stupid as a Shamanist Empire.
Pfahahahah, especially when someone declares Subjugation of Natives and conquers ALL OF EUROPE in one war b/c the converter gives you 0 tech and new world tech group. All all this disparity formed magically over the course of one day (CK2-->EU4). Sorry, it just made me laugh pretty hard.