User blog comment:Way2manybeer/Special war potentials/@comment-4822693-20130704131627

I think that the special war potentials are people with unrealized ability who are capable of being turned to either the quincy side or the shinigami side. In addition they have to be people with the potential to become as powerful as the royal guard. That is why there are 5 special war potentials, one for each royal guard member.

Ichigo --> At the time had an incomplete zanpakuto and he also has the potential to become a transcendental being. He's probably the number one opponent on this list.

Aizen --> He is immortal and no longer has a zanpakuto. However his zanpakuto was the most powerful illusion type in the SS and probably in the history of the SS.

Kenpachi --> He has arguably the greatest spiritual pressure of any soul reaper. However he doesn't know the name of his zanpakuto, and at the time that he was named a special war potential he was unconsciously suppressing his own strength.

Other possible people:

Ganju Shiba --> He's been training probably since the events in the invasion of the soul society arc. He's also a member of the Shiba clan, who apparently has some of the strongest and most talented members.

Komamura --> He is apparently of a very special lineage, and because of that he has the ability to access some as of yet unknown technique. This technique must be pretty powerful, because it looks like he is going to try and use it to gain back his bankai, so he must think that it is roughly as powerful as bankai.

Uryu --> Apparently he is more powerful than we have given him credit for in the past. It's possible he possess some kind of special ability.

I think that the reason why the quincies have to find people like this is because the Royal guard are very powerful, even more powerful than Yamamoto. They can't let the SS gain any more warriors at this level of strength.