This is kind of a lame reasoning, but I think it makes sense:
I would argue against anything that tries to vary Rey’s lightsaber from Kylo’s, because if it looks somewhat similar but ultimately different, it’ll feel like a fan edit trying to replicate Kylo’s effect, but not being able to make it look right. Personally it feels cleaner to go the kewlfish/Luka Frik route, which seems legit to my eyes, rather than something that falls into sort of an uncanny valley territory.