It seems like a minimal amount of work and it will make the server-side implementation of reliable websites much simpler. Also SRV records have been around for years...
Is there something I'm missing here?
Edit: @DJ Pon3 - what I'm talking about is:
one site served from two datacentres without needing BGP, but still working if either datacentre goes offline. (Can also be achieved by short DNS TTLs.)
multiple httpS servers on different ports on one IP address.