I don't think
Isobel looks very attractive. That o just ruins it.
Isabel is okay. I don't think
Izzy is inevitable, and probably an
Isobel would grow out of it eventually.
Belle is just gross to me.
I wouldn't use
Charlotte for a middle name if I had my heart set on using
Charles later on. If I did use
Charlotte, and then had a boy, I'd just suck it up and not use
Charles.