Gladys maybe could come back, especially among Latinos, who seem to like -ys names.
Wanda is years away from being hip again.
Gladys (5/10) - Has a certain hipster vibe to it. I could definitely warm up to this. I wouldn't a name a kid this now but in a few years it could seem fresh.
Wanda (1/10) - Just an unpleasant name that makes me think of unattractive older ladies.
Rhoda's in the same category.
Gwendolen (7/10) - I'd prefer
Gwen, but
Gwendolen's okay. It's definitely the most usable name on your list.