I'm just saying that in the public's concious,
Nikki is already firmly cemented as a NN for
Nicole. You could still use the NIK sound, I think; I'd just spell it a different way to help remove the
Nicole connotation.
I knew a girl named Michaelina NN Mici (prn
Mickey), so the Nici spelling was my first suggestion. Nicci would work, too.