I think you're right, it's nice but feels old-fashioned.
Francis (m) seems more appealing to me - both
Frances and
Francis do have a sort of chilly, cerebral, demure, even 'edgy' vibe, which seems a little less modern on a woman. I think you're right that it doesn't need a nickname.
My mother's best friend is named
Frances and she has always been known as
Fran. (Born around 1939) I like
Fran. It's casual but not cute, not aggressive and artificial like
Frankie, and not floofy like
Fanny. It does sound dated, like the 1950s, but I think it's unexpected rather than blowsy. Like
Jean.
Franny /
Frannie is another option but I don't like it - I just don't like the anny sound in any name.
- mirfak