Thats very interesting.
I do wonder how its gonna work - as in: if those girls that receive the Priority upgrade, become a "Proper" 6* (means, stats, stat increases, active, and passive skills powered up to represent the 6* status), or if they be like Alstromaria, where its just a cosmetic 6*, though granted she does have 4 passive skills which is very very rare for 5* to have.
Hmm upping Nadeshiko chan to 6* would turn her into monster like Safron... maybe even better since she has Life Drain activate.
Although... Honeslty.... 6* Sasanqua ...moff ... just thinking out loud mof mof :3