If God is Omnipotent, God can save all
One might wish to see the connection between omnipotence and the possibility of universalism; the connection is not esoteric. The argument is pretty straightforward:
1. Suppose God is omnipotent.
2. If (1), then whatever God does by means of a creature, God can do immediately.
Thus, (3) whatever God does by means of a creature, God can do immediately.
It might be of interest to note that Aquinas, Scotus, and Ockham, among others, hold to versions of (3)--though (3) did not go without challenge from some quarters. Still, (3) is by no means an oddity in the tradition of Christian thought. What is its significance?
Considering God's ordered power, we might say that this or that sacrament is efficacious in sanctifying or leading to some condition, C. Likewise, we might say that God saves, on condition of one's accepting Jesus as Lord and Savior. In each case, God is doing something by means of at least one creature: operating through sacraments or through one's consent. Such operation, I should think, is the normal order ordained from eternity by God.
But the normal order ordained by God does not bind what God can do. Speaking of God's power absolutely, God can save without operating through sacraments and without any creature's consent. And likewise for any contribution made from the creaturely side.
I suppose it is true that (X) we have sufficient knowledge of the normal order--so that the church can carry on here below--but that (Y) we do not comprehend the normal order. (X) and (Y) are logically consistent, and together imply that the church cannot be sure whether or where God acts beyond what we know of the normal order.
of course, one point that might still be made in all this: there is a connection not just between forbidding CWOB and stepping away from the cognitive content of the creeds on the nature of God, but also between denying the possibility of universalism and stepping away from the cognitive content of the creeds on the nature of God.