Congratulations, Blade! So happy for you!
I truly love so many of the names you have listed. My favorite of your firsts are Anastasia, Cosima, Melisande, and Rosamond. Of your middles, I'm pretty much enamored by Apolline, Chrysanthe, Eirene, Noor, and Solenne.
Thoughts thus far
Aquila - I have a strong association with this one, so it's hard for me to look at it objectively. I think it is a great match for you though. Such a strong name
Averill / Everild - I like this a lot, but it just doesn't seem to mesh with Antoine for me
Anastasia - So, so lovely. Smart, feminine, and sophisticated
Aristea - The imagery with this is fantastic. It feels so regal.
Constance - I feel like this has a bit of a hipster vibe, which is not necessarily a bad thing. She would make a lovely sister for Antoine.
Cosima - one of my personal favorites
Cyrielle (prn. with hard K) - As lovely as this is (and it is stunning), the pronunciation problems would bother me
Cyrielle AmbrosineEndellion - Again, feels like a departure from the romantic, latinate Antoine.
Evanthe - Stunning
Lucienne - So sweet and lacy. Do you think she'd end up a Lucy, though? I think I may prefer this in the middle.
Melisande - Another of my personal favorites. Queenly is certainly the best word to sum it up. Depending on your pronunciation, there is a bit of assonant rhyme with -sande and -toine though
Meriel - I love the sound, but it just doesn't stand out as much as your other names
Myriam - Miriam/Myriam definitely deserves more love. However, she just feels a bit plain next to Antoine.
Nerissa - I love how feminine and somewhat exotic this name is. I love the literary flair and it just seems like a good fit. Would be great with Antoine.
Rosamond - Has pretty much all the most excellent qualities a name could have. Strong yet melodic sound, wonderful meaning, deep history, recognizable yet unexpected. Just rather perfect. Also, I think this is stunning with Antoine.
Sunniva - Nice, but not my favorite from your list.
Sylvia - great, underused classic with an aura of intelligence and refinement
I also love the suggestion of Renata and think that Ines would be a great fit for you.