Although I dis not see SAM as a real contender for the Benefactor, because I would find that extremely lame and far fetched considering how SAM has behaved so far, there is something I remember about Alec Ryder.
He reasoned that a symbiotic relationship would stop the threat of AI as the AI is part of a being and therefore not an enemy but part of itself. However, I do find that a bit naive since SAMs can be transferred from one person to another and therefore can sabotage a host and then jump hosts. We can't really assume that an AI with all its intelligence wouldn't be able to figure that out.
I mean, for all we know SAMs ultimate purpose is to join up with Ellen Ryder and the other Ryders are simple vessels to be used until that's possible. It could've been a directive from Alex that got a bit too engrained in SAM.
So yeah, if that were the case I could actually follow what SAMs been doing so far.