As has been discussed before, the use of redcaps by the order raises the question of why an order of wizards need messengers who travel by road. Why don't the redcaps use Leap of Homecoming to jump between covenants instantly? Why don't magi communicate via Haunt of the Living Ghost (ArsM5, p.144) or use a Creo Mentem effect to speak into someone's mind?
One of the main responses to this is that these alternative forms of communication involve arcane connections, and magi would not want an AC to their covenant carried around by a redcap who could be kidnapped, or in the hands of another covenant they may not trust, and even more so with an AC to themselves.
However, I am wondering if there would be a system that involves an AC to a neutral entity.
For example, covenants could swap ACs to a mundane employee, perhaps someone who lives outside the covenant, and then messages could be spoken into that person's mind and he/she is paid to deliver those messages to the magi (who could, perhaps, read their mind to verify the accuracy of the message).
Alternatively, an AC to a room could be used with a Muto Terram effect to write a message into the wall, which would then disappear when the spell expires. Perhaps this could be at a central location where redcaps live, and one is always on duty at the wall. When a message arrives it is copied and sent out, dramatically reducing the distance needed to travel to collect then deliver a message.
Any problems with these ideas?