NCB,
“He seems to be working off the assumption that all Baalei Teshuva and Geirim refrain from wrapping tefillin on Chol Hamoed. I think this has come up in the CR before. It is totally mythical; I have no idea where the idea originated. There is no such thing as a specific mesora for non-FFB’s. A better question would be, do minhag haGra folks have to wrap tefillin in KAJ to not be over on lo tisgodedu?”
I got this idea from talking to and learning the seforim of HaRav Moshe Sternbuch. We were members of his kehilla in Johannesburg, and I asked all my big shaalos to him when living in EY. It’s not that there is a mesora for non-FFBs, but as i wrote above someone who doesn’t have a minhag, would take on the minhag of his Rav/Rebbe (I didn’t write that earlier but i should’ve) or default to the halacha as paskened in Mishna Brura.
Maybe it can be compared to waiting 3 hours from meat to milk. It is a major kula, but accepted in many kehillas. You can’t just decide to take it on because many other great people accept it, without having it in your mesora.
Regarding a Gra-nik in KAJ, I imagine they build a special area in the shul cordoned off from the tefilin wearers, and give them special piyutim to say with the notes to sing the nigun in the correct nusach.