What do you mean, can you entrust one domain with multiple registrars?

Splitting them round robin, or even in half, sounds horrible.

But maybe if you have 1 (one) backup domain like mydomain.net then you can host that on another vendor. But I'd rather just fail and focus on restoring at that point, you are still losing all traffic to the main domain, and contacting users with a secondary domain they've never heard off is a security posture nightmare and unprofessional.