Hmmm. Been debating trying a Gambler Satori after I beat the final boss. In postgame she can have the max mp for "Small MP Recovery" to really shine, and won't have a large mp detriment on ally skills, and Gambler would give her the means to turn any strong move into a real nuke. Honestly, with a main equip to boost max mp, she'd probably have very few mp troubles even as Gambler, and Trauma Recollection+flexibility with weakness hitting would help her be useful against any boss. The question is if it's worth dropping Flan...
As for Byakuren Carry, she does have the self-buff stuff keeping her going, but in my experience her actual attacks aren't quite as strong as you might think. The main advantage is just that she has a variety and they carry debuffs/statuses, and that she's in general a good character with her passives, but... I think other people are better suited, other than Byakuren's durability getting boosted by having permanently high buffs. Sakuya Carry would depend on SDM to really work, but if you were doing Sakuya Carry you'd probably use them all already anyway.
Yukari actually -would- be a pretty cool carry, since she has -very- good passives like Border of Strength/Witchcraft and her regeneration passive (and majesty) and a good team passive. Ran is a useful support to have boosted with her and then Chen is... huh, Ran buffing her evasion, I wonder how useful 200+ evasion is?