The Big Universe (Tegmark 1) is much easier to accept than level 4, as it is the current scientific consensus on cosmology.

BTW, I strongly believe (>90%) that the consensus on cosmology is will change in some way that doesn't have strong implications for observations but does have strong implications for this kind of philosophy. E.g., the dark matter/energy problem getting resolved to some way that makes the universe finite.

As for level 4, we could have a long and pointless debate that would reduce to the subtleties of defining what it means for something to exist.