I like
Eleanor,
Elizabeth,
Martha,
Nell and
Bess. Dislike Mittie. I'm not generally a fan of longer names with nn so I would usse any of the names in my like list as full names.
Here are some nn for Classic names I've heard - they're probably too common but theY have the double letter so here goes.
Veronica-Ronnie
Mildred-Millie
Olivia-Ollie
Emeline-Emmy
Esmeralda-Esmee
Mary-Molly
Dahlia-Dolly
Margaret-Peggy
Dorothy-Dotty
Priscilla-Cilla
Linnea-Linny
Tabatha-Tabby
Abigail-Abbey
Anabelle-Annie/Belle