Simpler. I set up my personal email on a domain I own to forward to my gmail account. In gmail, I "claimed" my email (it sent me a message with a link which I clicked). After that, I can send from gmail and Google will sign it as coming from my personal email (on the domain I own).
I do the same thing and I run a postfix server to reforward the mail to my gmail account after it hits my domain. I actually don't have any redundance or backup server-side and rely on the mail client to sync content to disk. While Google disabling my account may put me out for a short time, it will only be however long it takes to reconfigure postfix to actually store my mail (or forward somewhere else) instead of just forwarding.