I'd like to setup a DNS server that acts a secondary authoritative server in case the primary goes down. Normally, that'd be easy to accomplish with AXFR, but I want it to be secondary to CloudFlare, which doesn't offer zone transfers. Is this possible using existing software? I'm planning on attempting it with BIND9, but anything reliable will do.
In theory, the server would just need to act as a combination of caching, forwarding, and authoritative servers, all for the same zone.