To add regarding Gracie, there's also the whole "mystery of her blackout in the woods" that everybody keep in hush, hush and tries to keep Gracie in the dark about. That may not be as significant as My name is Luna storyline, but I'd wager that has some emotional depth to it regardless.
Isabel, I wholeheartedly agree with you. While the whole tease between MC & Isabel may be a bit on the basic side in terms of character interactions, Anonio feels like the wild card that can really drive her narrative forward.
Cordia, well......there's a whole bunch. Major crux for her would be the whole reconciliation between her & Luna (and her feelings of guilt), her reluctance to involve Gracie to the Family business (which I hope to see some of Cordia's meaningful interaction in the upcoming update, even though it's pretty much Gracie's arc).
And that's just for Cordia's interactions with her daughters. Weaved in between those events, and added additionally, we'll get to find out the real woman behind the "Blizzard Queen" moniker.
Game feels like it's going about each of the girls' routes in a very distinct & unique way, and I'm really looking forward to it.
p.s. Above is only the main girls. There's also girls like Eiza, Charvi, Amita, Amata, Caterina, Lelianna, Siobhan, and more which while we probably won't get traditional routes like our mains, we'll still get some decent interactions with.
But regardless, it's gonna be good.