We've talked about Nikola or other variations for a girl as well, but I am less fond of them.
I was really anti nickname when we named our first, Tristan. I have never liked people taking liberties with my name ( in my case, they called me Tabby instead of Tabitha) and generally prefer not to shorten other people's names unless they insist.
But here we are with 4 kids and while we don't shorten Tristan we call our others kassi (Kassiopeia) Toly (Anatoly) and Rome ( Romneya) because they like their nicknames. I imagine if we have a boy we will call him Niko at least sometimes.
We must choose a saint name, so we spend a lot of time perusing the calendar of saints.