Haha, it would also be kinda interesting to have @allegiance, but very far from useful in the least bit.
It's funny. I was talking to somebody about it and they wanted @trade for the same reason you did: to separate random chat from business. I want it for the opposite: to separate business from random chat
When you bring up the points that you did about @alliance, it made sense. However, how does one expect to get the parties set up without a good method of communication between the alliances?
Vent would work, but people like me aren't always able to use it and prefer more textual methods.