It’s very neat. I was probably giggling as I sent emails back and forth to myself.
My only comment at this point, is that the bridge sends the email using your public key and the bridge’s domain, as you point out. So you’re still stuck in the centralized idiom and can’t easily switch to using another bridge. To the email server, your identify is tied to the bridge.
Disclaimer: I don’t really understand how the bridge works so my knowledge is probably flawed.