For Thomas, there are four identity claims for God and simplicity.

1. God is not distinct from his nature.
2. God’s properties are not distinct from one another.
3. God’s nature is not distinct from his existence.
4. God has not properties distinct from his nature.

Now, I’m not a proponent of the doctrine of simplicity, I think it has its problems.  However, I want to consider the fourth claim.  The problem with the fourth claim is that it claims God is immutable and possesses no accidental properties.  Consider the actual world.  I’m currently wearing khakis, a dress shirt, tie, sweater vest, and glasses.  Suppose in another possible world, W, I am wearing jeans.  In world W2 I am not wearing glasses and I’ve got perfect eyesight.  In world W3 I don’t even exist.  In these worlds no obvious contradiction obtains.  I think it would be quite difficult to deny these worlds as being possible.  Given these possibilities it seems that God does have accidental properties when considering worlds W-W3 as they relate to the actual world since God’s knowledge and relation to me in these worlds would very (accidentally).

Perhaps, if the physical reality does exist in a manner of some form of the multiverse (at least Level 2 or greater) then God may perhaps be simple and this objection may not hold.  Thomas’ lack of distinction between properties may hold true and what appears to be accidental may just be a form of the actualization of the whole essence of God.  Perhaps all worlds W-W3 are actualized, either previously, presently, or in the future.  This, of course, doesn’t necessarily suggest that every possible state of affairs are actualized, it merely commits to the actualization of God’s essential desires/nature.