Hi @BlueAnanas,
Your best option for a more immediate solution would be to make use of the outgoing webhooks and build some sort of small hosted application that will receive the events anytime @mailer (or some other trigger word) is at the start of a message and the compose the email just as you like it, and fire it off to your distribution list.
That said configurable mention email subjects and bodies is something that I can see being useful and if you'd like you can submit a feature request here for that.
If you were to configure a single mailer user then you could change that user's notifications to only go through on mentions. You can do this in Account Settings -> Notifications -> Words that trigger mentions and click off everything but the mention field.