With a completely separate architecture that also loads the root zones in a completely different way?

It's certainly possible to do. Public recursive DNS isn't that big of a spec that you can't have two independent teams doing it, and mandate they do things differently when possible. Run the two /24s on different ASNs, too.

I've had sales teams pitch me on their authoritative DNS service running heterogenously, although I guessing both partitions gathered config from a single place, but we didn't get that far in the potential customer pipeline.

Of course, just because it's possible doesn't mean they're likely to do it.

Maybe also run by a separate company with a different CEO for additional redundancy. :) so now we've got 1. and 8.

Best to service from a different planet, in case something happens to this one.

I hear Musk has been working on that. (j/k, 40 min ping time...)