It would be useful to be able to access the Inbox custom fields when adding template variables into signatures, so that we could have one signature that pulls in inbox-specific information.
Right now we use Account custom fields for a similar purpose, but this confuses our users because those fields don't appear until there's an account-linked contact added to the To field of a new message.
Would love to see this feature too.
Our use case is applying different telephone numbers and opening hours based on Inbox custom fields.
The same operator might reply from IT support or Operations but the two departments have different phone numbers and availability hours.