Board Thread:Questions and Answers/@comment-10797017-20130627100621/@comment-11051098-20130705142935

Aizen was one of the original war powers, I'm sure Yhwach stated that after he visited him in Muken.

However, both Kenpachi and Ichigo have got great power-ups since the last invasion. Kenpachi have unlocked his full potential, all of which he have unconsciously suppressed, and Ichigo have got a "real" Zanpakutô and have unlocked his full potential as well. So I think they will definitely remain Special War Powers.

I wonder if the remaining 2 could be Royal Guard members, as their total power is said to surpass the entire Gotei 13. Maybe Kirinji, he taught Unohana healing spells in the past, and including his healing hot springs, he could be regarded as a master healer. Taking out him could be a goal, if the Vandenreich knows about his healing springs and skills.

However it's not certain they can even touch him in the first place, when he apparently is the greatest Shunpo-master in the Soul Society.