1. Kurama: Strong chakra due to Uzumaki Clan bloodline. Skilled in sealing jutsu, particularly Adamantine Sealing Chains which can subdue tailed beasts. Kurama sealed Nine-Tails during the Konoha attack. His inclusion in Akatsuki would greatly help in the Tailed Beast collection. 

2. Fugaku: Unmeasurable strength. Activated rare Mangekyo Sharingan willingly during the Third Great Ninja War. Itachi believed Fugaku's power surpassed his.

3. Third Raikage: Considered perfect Raikage. Sacrificed himself to fight thousands of enemies and protect his teammates. Rest would have altered the outcome. Having him in Akatsuki would make collecting-tailed beasts easier.

4. Hōichi the Sage: Wields a biwa. Helped separate tailed beast Matatabi from Jinchuriki. Fought two-tailed beasts alone during Chunin Exams. With him in Akatsuki, collecting tailed beasts would have been quicker. His unique ability, Sealing and Absorption, would aid Akatsuki.