As per your request I started working on tag support. My idea is if someone run the below command in a slack channel X then X itself will be subscribed to the tag support.
subscribe:tag support
Here every clients should configure outgoing webhook on slack with URL(s), Token and Trigger Word(s) fields. Trigger Word(s) should be configured as subscribe:, unsubscribe: etc., or we can give common name like discourse:.
Now what is your opinion @mcwumbly?