The self-host dream for me is a relay that will automatically connect to all in the inbox / outbox relays of people as well as defined relays, proxy on demand but also cache what it proxied so that if an origin server goes down it still works. Store events sent to it on top of that, as well as forwarding those to all the outbox relays. Software like that sounds like a dream for this ecosystem as it then becomes much more decentral if all these relays are proxying to each other. Yours is so close from the sounds of it, but you have that 1 account restriction on it.
Discussion
What do you need? Support for multiple npubs *of your own* in one subscription?
Its not a need really, I am just toying around and probably wont host. But I like having the skills to setup infrastructure of communication should I need to. Lets say Nostr becomes blocked and I want to spread info on how to self host these. Knowing which relay can act as a peer in an unreliable environment is big. Because those then interact with the bigger relays as a proxy but also serve as a local relay in situations where the upstream ones become unreachable.