Nice. Very detailed, and well thought-out. It occurs to me that their major flaw is dependent on sleep...which gives an inherent advantage to a Warforged Soul Keeper...

I do have a couple of questions (and if these have already been answered and I missed it, I apologize in advance):

First, the process for filling soul charms is described under Extract Soul. However, how do you empty a soul charm? I assume it must be possible, since you can benefit from Acquired Soul a number of times equal to 2x class level, but you can only have a number of filled charms equal to 1/2x class level.

Second, how long does an exhausted soul take to recover? It can be shortened with Revitalize Soul and Restore Soul, but I don't see a base time. Do they restore whenever the Soul Keeper gets his 8 hrs of sleep? If so, that would neatly sidestep the problem of sleepless Keepers never having to deal with the Overwhelming Thoughts flaw...