[Deregibus]

I was thinking the same thing. Assuming it's technically feasible I don't see this as being a huge problem. If your site is important enough that you can't have any downtime due to a CA revocation then you spend the extra time/money up front to get get cross-signed certs. If you don't care, then you just fix the problem when it comes up. If CAs start getting revoked more often then this will just become standard practice.