I adore
Clemence, either pronunciation. My only fear is that in English someone will think it's pronounced like the word clemency, with an "ee" sound on the end.
Clemence brings to mind a Parisian cafe street scene, or an extremely intelligent writer. But clemency brings to mind prison parole boards. Not what I want associated with a name.
So as long as pronunciation isn't an issue, I'm all for
Clemence. As much as I love
Clementine /
Clementina, I think I love
Clemence even more.