I don't understand why you would give a child a name and decide beforehand not to use it. If you're not going to use it, I would make it a honouring middle name.
I love the name
Catherine, but spelled
Katherine so would use it as is. But I also like the nns
Kat and
Kata, but have found with my own children that nns usuaully evolve unexpectedly, so wouldn't plan to use a specific nn.
Have to say I hate
Kitty, but I hate girly, cutesy names.