Hm. So, if I get the idea correctly, we exist simply because it is possible to construct a mathematical model of our universe - we are that model.

Here's where it gets interesting for Atheists: if it is possible to mathematically describe a model of a theistic universe, then one must exist.

Contrariwise, if a theistic universe can be shown to be mathematically impossible (which is to say, it is provable that no such model can be constructed), then there's no God anywhere, nohow.

The latter seem like it could a worthwhile pursuit - to attempt to mathematically describe systems with the properties required for theistic universes and perhaps even coming up with testable ideas concerning to properties of theistic universes (and I mean beyond Archibald MacLeish's "If God is Good He is not God, If God is God He is not Good").

Just having fun, mostly.