As for the sync rank, I used that.
Unknown variables must be taken specifically in case of core. Iori, who completed ByakuShiki has to insert a lot of cheat codes and remove it one by one when Ichika's proficiency increased
Kurogane can't have Reiryaku Byakuya, despite being an upgrade of KureZakura, unless it's used by the Orimuras. On the other hand, ByakuShiki has it despite being based directly on ShiroKishi (who can't). So it's really core-pilot specific, with frame being the buffer.
EDIT: Oh wait, It also incorporates Yukihira... hmm....