1. Gellius, no contest.
2. So long as you find her insta-skill useful, keep her as is. Improved stats are great, sure, but not quite as game-breaking.
3. With Gellius as a full tank and Olivie for emergency use, I'd say SAW Anya.
4. i dunno lol
5. I don't have Nanaly myself, but i hear two are better than one.
6. Of only those, I'd prioritize Iris, as Fedora kinda overlaps with Chydis' role (+range on skill). However, consider AW some non-Healer healers - say, Pippin from the recent event, or Sera from the current one.
7. Fran has better stats, but Vincent will (hopefully) soon get his absurd SAW. I'd go for the latter.
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Well, Cloris.