Okay, so names that are similar to those on your list…
I think [name_f]Felicity[/name_f] and [name_f]Verity[/name_f] are definitely the best of the -ity names, but there’s also [name_f]Serenity[/name_f], [name_f]Charity[/name_f], [name_f]Clarity[/name_f], and [name_f]Amity[/name_f]. And I just thought of [name_f]Carys[/name_f], which isn’t an -ity name, but has such a nice meaning, “love”.
[name_u]Meredith[/name_u] makes me think of [name_f]Morwenna[/name_f], [name_f]Morgana[/name_f], Asenath, [name_f]Tanith[/name_f], [name_f]Edith[/name_f], [name_f]Ferelith[/name_f] (too bad your sister loves [name_f]Faye[/name_f] so much; [name_f]Ferelith[/name_f] nicknamed [name_f]Faye[/name_f] would be pretty), and [name_f]Gwenyth[/name_f].
I love Greek girls names that end with the -ee sound, so if [name_f]Ariadne[/name_f] and [name_f]Penelope[/name_f] aren’t quite it, there’s [name_f]Danae[/name_f], [name_f]Calliope[/name_f], [name_f]Selene[/name_f], [name_f]Persephone[/name_f], and [name_f]Nephele[/name_f]. (Along with the more common [name_f]Zoe[/name_f], [name_f]Chloe[/name_f], [name_f]Daphne[/name_f], and [name_f]Phoebe[/name_f], of course.)
If you like [name_f]Victoria[/name_f] nicknamed Vix, what about [name_f]Beatrix[/name_f] nicknamed [name_m]Bix[/name_m]? And I think I remember reading somewhere that the original version of [name_f]Beatrix[/name_f] was Viatrix, which would also be pretty cool.
I love tfzolghadr’s suggestion of [name_f]Ottoline[/name_f] to get to [name_f]Lottie[/name_f]. [name_f]Lottie[/name_f] feels a little more instinctive as a nickname for [name_f]Ottoline[/name_f] than [name_f]Ottilie[/name_f] (although I think it works for her, too) and [name_f]Ottoline[/name_f] is easier to pronounce.
[name_f]Cordelia[/name_f] has some great nickname possibilities: [name_f]Cora[/name_f], [name_f]Delia[/name_f], [name_f]Della[/name_f], [name_f]Lia[/name_f], [name_u]Corey[/name_u]. [name_f]Della[/name_f] is similar to [name_f]Nellie[/name_f] and [name_f]Adele[/name_f]/[name_f]Adela[/name_f], so I particularly like that one for you, although I’m not sure how I like it with Da1sy.
Speaking of [name_f]Adele[/name_f], there’s also [name_f]Adelaide[/name_f], [name_f]Adelina[/name_f], [name_f]Adeliza[/name_f], and [name_f]Adelia[/name_f].
If none of the -ska names are working out as a formal name for Skye, then maybe a sky-related name? Celia, Celeste, Celestia, Celestina? Oh, or my personal favorite guilty pleasure, Scholastica! I kinda love Scholastica nicknamed Skye now…
You would lose the fun February connections, but instead of Iolanthe, what about Chrysanthe? You would still have the -anthe part to honor Ethan (and maybe there’s a birthday or anniversary in November you might want to honor?). Or maybe Anthea? I could see Anya working as a nickname…for any of those names, actually! Would that make Iolanthe more wearable?
Anya would also work for any Anna- or -anna name.
And just some random suggestions:
[name_u]Vesper[/name_u]
[name_f]Isolde[/name_f]
[name_f]Lorelei[/name_f]
[name_f]Rhiannon[/name_f]
[name_f]Sunniva[/name_f]
[name_f]Gwendolyn[/name_f]
[name_f]Endellion[/name_f]
[name_f]Mathilda[/name_f]
[name_f]Odette[/name_f]