I actually don't mind the use of the letter X in place of the letter Z. - in genral
BUT
In Xoe it aint cool. Everyone will just spell it
Zoe or
Zoey and that will just stink. It's too popular to change the spelling without it just being a silly -and lame- attempt at "different". Xane seems kind of pointless but at least it isn't in the first name slot...