I know a Felicity and the diminutive that naturally emerged for her was Fliss. I've heard of that used on other Felicitys as well, and also Flick. Don't worry too much about nicknames I would say, if you're a nicknaming sort of person they'll probably emerge naturally for most any name you pick, and especially a 3-syllable name like Felicity. Do you like Felicity otherwise? I think it's a really nice name! Felicity Claire is lovely.
From the examples you give I think your two styles seem fairly similar - the vibe I get from most of them is classic, unpretentious, sophisticated, though maybe he's a bit more conservative than you? You each picked a few of my aunts' names out (which all seem to get a lot of positive comments on this site) so maybe you have similar taste to my grandparents, so I'll include the other sisters ;)
Feli (fell-ee) and Cita (see-tuh) are two natural nicknames for Felicia/Felicita, which is the Spanish version of Felicity.
Thank you for the suggestions and for including some nickname ideas.
I pretty much like or love every name you suggested! Haha! Many of these I have suggested before and I just get an okay answer from my husband.
Arielle/Ariella (Elle, Ella, Ellie, Aria)
Coraline (Cora, Cori, Coral)
Camille (Cammy, Milly, Mila)
Genevieve (Gen, Vivi, Viv, Geni, Genni, Jenny, Jen)
Gwendolyn (Gwen, Gwendy, Wendy)
Isadora (Izzy, Dora)
Theodora (Thea, Dora)
Josephine (Josie, Jo)
Catherina (Cate, Cathy, Cat)
Marigold (Mari, Goldie)
Magnolia (Maggy, Mag, Nolie)
Lucinda (Lucy, Cinda)
Annika (Annie, Ann)
Arabelle/Arabella (Belle, Bella)
Miranda (Mira, Randi)
Angelique (Angel, Annie)
Angelica (Angel, Annie)
Anneliese (Anna, Annie, Lisa)
Rosalie (Rose, Rosie)
Rosalind (Rose, Rosie)
Alexandra (Alex, Lex, Lexi)
Amaryllis (Amy, Rilla)
Camelia (Cam, Cammy)
Francesca (Fran, Franny, Frankie)
Hey, I can help, I have a daughter Felicity!
Honestly, every day I love her name more and more. We get compliments on it constantly, and the nickname that my husband came up with and that we now use tons of is "Lissy". It's a really sweet little baby girl nickname and I love it, it fits her perfectly and it's so sweet when she says her own full name. Right now her older sister is yelling "No Lissy!" and it's still great haha.
Like others mentioned, there is also Flick which is common but I've never used. I don't recommend Felly, yucky, imo!