Feathers

So with my Fir and Catria merge projects for my arena core now at +10, sadly Micaiah is 5* locked so she's stuck at +6, and now that I've gotten Witch Mia both Gravity+ and Pain+. I'm not sure what to use my 25kish feathers for next as I'm not really looking to work on merging again at the moment.

Options could be:
Finally promote Julius, Lyon, or Aversa (although I have +atk/-def Summer Tana who I'd probably rather use).

Promote better iv Soren (+spd/-hp).

Get WF!Hinoka a Brave Bow+, would still opt for her prf in most situations but there may potential to cheese maps with BB and flier mobility? Also nice hone boost from Mia.

Or give Witch Mia some A or B skill that I currently can't think of but maybe someone can point out that would require feathers to get. Currently she has Spd/Res Bond and Wings of Mercy.

Thanks in advance for any suggestions!