I think that this is a good scenario of when things can align perfectly. Since your mother goes by
Jo, and you would be using
Josephine in full, I imagine, then you get the best of both worlds. Your child can has their own distinctive name without feeling put upon to live up to a name, while the honouring connection is still quite clear. I think you're golden!
(And don't feel bad about fretting over this stuff - I am always warring with the issue of honouring-vs.-individuality and which should be more important with my own names!)