That's a pretty cool approach! I'd only be worried about the risk of leaking the main account address when responding to anything, but it's probably doable with a bit of research, like Postfix catch-all setups seem straightforward enough.
FWIW that should just be a matter of using the right configuration and mail client. With Fastmail for example I get to use a catch-all setup with my domain, and respond to whatever email it was sent to.
And the other way around as well. Send an email from an arbitrary <whatever>@domain email address.
