Someone who holds this view would probably have to make the definitions more precise, so that if you live in a deterministic reality, you actually cannot conceive of a universe that isn't deterministic. You can throw around words like "indeterministic", but you cannot precisely simulate something indeterministic using only deterministic ingredients, and hence, for some precise definition of "conceive", cannot conceive such a universe.

If one assumes paradoxes are impossible maybe.

The author's tenets seem to insist upon the reality of universes expressed in inconsistent formal systems, so I don't think this is fatal to the argument - though it suppose it might render pointless any attempt to treat the premise analytically.