Start on NXT but then continue on Raw/205Live/CW Division. Have a blood feud in NXT through Brooklyn but don't have the blow off happen at Take Over, have Ciampa win underhandedly or cheaply via roll up or something so fans and Gargano don't get their complete revenge. Then have Ciampa called up/signed to 205 Live based off this win, so Gargano unable to continue the feud for a spell.
This time separated would give Gargano time to focus on NXT title with the idea that it is a pathway to the main roster and his path back to getting his hands on Ciampa.
They came together in NXT. The won Gold in NXT. They became friends in NXT. And the betrayal took place in NXT.
I'm not going to act like the level of storytelling NXT is anywhere it used to be, but this is one thing they've done incredibly well and they should keep going with this story on NXT into Takeover Brooklyn where true, raw emotion can be experienced.
On Raw it would be treated as filler and on 205 Live it would be like it barely exists.
NXT, absolutely. I wish the feud would culminate in an NXT title match between the two but that's probably not very likely, at least they have a potentially brilliant feud to go along with the top title feud. The two will kill it.