[name_m]Hi[/name_m] there.
[name_u]Jasper[/name_u] [name_m]Hugo[/name_m] nn [name_m]Jack[/name_m] is adorable. And [name_f]Lucille[/name_f] [name_f]Violet[/name_f] is so lovely! [name_f]Nora[/name_f] would be amazing for her sister. [name_f]Do[/name_f] you like [name_f]Eleanora[/name_f]? Maybe [name_f]Leonora[/name_f] or [name_f]Lenora[/name_f]? Maybe [name_f]Anora[/name_f] spelled this way appeals to you more. I find that nicer looking than [name_f]Honora[/name_f]. Although for I can try to sell you on [name_f]Eleanor[/name_f]. It’s one of my top three favorite girl names. I used to not even care for it. One day a couple of years ago I heard a little boy call to his big sister [name_f]Eleanor[/name_f] at the children’s museum. The little boy was called [name_u]Finn[/name_u], which has been one of my favorite boys for 20+ years now. [name_m]Just[/name_m] hearing the sib set together made me see [name_f]Eleanor[/name_f] in a different light. [name_u]Finn[/name_u] is so rough & tumble witty outdoorsy & sporty, that it just made [name_f]Eleanor[/name_f] seem less dull & more running through a meadow picking wild flowers. Or maybe a little tomboy playing baseball. Either way, I love both of those imageries, & it made me fall for [name_f]Eleanor[/name_f]. Plus, I adore the nn [name_f]Nellie[/name_f] after my great grandmother. Does my rambling help at all? 
Here are my thoughts on the rest of your list-
[name_f]Dahlia[/name_f] nn [name_u]Dell[/name_u]-[name_f]Dahlia[/name_f] is gorgeous. It’s bold, beautiful. & sweet. It’s seemingly old fashioned? Simple & well known but not popular. [name_u]Dell[/name_u] isn’t really my cup of tea, but it’s a creative nn for [name_f]Dahlia[/name_f] that’s spunky & totally works.
[name_f]Mirelle[/name_f]/Mirabal nn [name_f]Mira[/name_f]-I’m a huge name nerd, & I still get confused on how to say/spell [name_f]Mireille[/name_f]. It may be tricky. [name_f]Mirabel[/name_f] is simply beautiful, & I really like [name_f]Mira[/name_f] too. Kind of different, feminine & lovable. But still short & sweet.
[name_f]Penelope[/name_f] nn [name_f]Nell[/name_f]-I really love [name_f]Nellie[/name_f] more than [name_f]Nell[/name_f] for some reason, but [name_f]Penelope[/name_f] is really fun & perfect w/Jasper & [name_f]Lucille[/name_f]. I like the nns [name_u]Penny[/name_u] & [name_f]Polly[/name_f] too. [name_f]Poppy[/name_f] also works, but too cutesy.
[name_f]Clarissa[/name_f] nn [name_f]Clara[/name_f]-I like [name_f]Clara[/name_f] a lot on its own, but [name_f]Clarissa[/name_f] nn [name_f]Clara[/name_f] makes sense. I’m just not into [name_f]Clarissa[/name_f]. It almost sounds 80s rather than classic.
[name_f]Arabella[/name_f] nn [name_f]Bella[/name_f]-I really like this, but maybe a no go w/your ln.
[name_u]Darcy[/name_u]-Not my style. Maybe because it’s kind of boyish…I’m not sure. Maybe it could be a nn for [name_f]Dorothea[/name_f]? I think [name_f]Lucy[/name_f] & [name_u]Darcy[/name_u] are fine for sisters.
[name_f]Cordelia[/name_f] nn [name_f]Celia[/name_f]-The nn seems a bit of a stretch. I like [name_f]Celia[/name_f] a lot though! [name_f]Delia[/name_f] or [name_f]Cora[/name_f] make more sense & are also very nice names. I actually love [name_f]Cornelia[/name_f] a lot more than [name_f]Cordelia[/name_f]. It sounds sweeter & less stuffy. And you could do [name_f]Cornelia[/name_f] nn [name_f]Nell[/name_f].
Here are a few more ideas. Sorry for any repeats.
[name_f]Annabelle[/name_f] nn [name_f]Annie[/name_f]/Anna
[name_f]Annabella[/name_f] nn [name_f]Annie[/name_f]/Anna
[name_u]Antonia[/name_u] nn [name_f]Ani[/name_f]/Nonie
[name_f]Abigail[/name_f] nn [name_u]Abbie[/name_u]
[name_f]Beatrice[/name_f] nn [name_f]Bea[/name_f]/Bess/Bette
[name_f]Beatrix[/name_f] nn [name_f]Bea[/name_f]/Bess/Bette/Trixie
[name_f]Bridget[/name_f] nn [name_f]Bridie[/name_f]
[name_f]Catriona[/name_f] nn [name_f]Cate[/name_f]
[name_f]Clementine[/name_f] nn [name_f]Cleo[/name_f]/Minnie
[name_f]Dorothy[/name_f] nn [name_f]Daisy[/name_f]/Dora
[name_f]Dorothea[/name_f] nn [name_f]Daisy[/name_f]/Dora/Thea
[name_f]Elizabeth[/name_f] nn [name_f]Elsie[/name_f]/Ellie/Eliza/Bess/Bette/Tess
[name_f]Emilia[/name_f] nn [name_f]Millie[/name_f]
[name_f]Estelle[/name_f] nn [name_f]Essie[/name_f]
[name_f]Frances[/name_f] nn [name_f]Franny[/name_f]/Francie
[name_f]Felicity[/name_f] nn Fliss
[name_f]Genevieve[/name_f] nn [name_f]Gigi[/name_f]/Ginny/Vivie/Evie
[name_f]Gwendolen[/name_f] nn [name_f]Gwen[/name_f]/Gigi
[name_f]Georgia[/name_f] nn [name_u]Georgie[/name_u]/Gigi
[name_f]Georgina[/name_f] nn [name_u]Georgie[/name_u]/Gigi
[name_f]Georgiana[/name_f] nn [name_u]Georgie[/name_u]/Gigi/Ani/Ana
[name_f]Greta[/name_f] nn [name_f]Gerty[/name_f]
[name_f]Harriet[/name_f] nn [name_f]Hattie[/name_f]
[name_f]Imogen[/name_f] nn [name_f]Imee[/name_f]/Idgie/Ginny
[name_f]Isobel[/name_f] nn Ibbi/Izzy
[name_f]Josephine[/name_f] nn [name_f]Posey[/name_f]
[name_u]June[/name_u] nn [name_f]Junie[/name_f]
[name_f]Jane[/name_f] nn [name_f]Janie[/name_f]
[name_f]Kathleen[/name_f] nn [name_u]Kit[/name_u]/Kitty
[name_f]Margaret[/name_f] nn [name_f]Maggie[/name_f]/Maisy/Molly/Peggy/Gerty
[name_f]Magnolia[/name_f] nn [name_f]Maggie[/name_f]/Mally
[name_f]Magdalena[/name_f] nn [name_f]Maggie[/name_f]/Lena
[name_f]Matilda[/name_f] nn [name_f]Millie[/name_f]
[name_f]Maureen[/name_f] nn [name_f]Maisy[/name_f]/Molly
[name_f]Rosalie[/name_f] nn [name_f]Rosie[/name_f]
[name_f]Rose[/name_f] nn [name_f]Rosie[/name_f]
[name_f]Rosalind[/name_f] nn [name_f]Rosie[/name_f]
[name_f]Rosamund[/name_f] nn [name_f]Rosie[/name_f]
[name_f]Susanna[/name_f] nn [name_f]Sadie[/name_f]/Sally/Scout/Anna/Annie
[name_f]Theodora[/name_f] nn [name_f]Thea[/name_f]/Dora
[name_u]Vivian[/name_u] nn [name_f]Vivie[/name_f]
[name_f]Wilhelmina[/name_f] nn [name_f]Willa[/name_f]/Winnie/Minnie/Mina
[name_f]Hope[/name_f] this helps. 