In Arcade in particular, some games (the one that I'm working on being most relevant to me) have all players set to neutral at the start of the game and use a single team in the lobby since it's a much cleaner presentation than 10 different teams with just one person each (which also ends up disabling Party Join). Unfortunately for the majority of my players, they're never allied with anyone, but still get Allied chat popping up as the default.
It would just be very helpful if there was a setting for selecting or prioritizing whether Allied Chat or All Chat is the default when simply pressing Enter to chat. It's not hard to Enter->Tab each time, but it is quite tedious, especially when the game involves a lot of communication.
I would imagine that such an option would actually be helpful to many players outside of Arcade entirely. If this setting were added for players, I would just be able to override it for my map so that All Chat comes up by default in the same way that the Simple Command Card setting can be overridden.
Given that the setting is merely a toggled option to change the order of a list, I can't imagine it would be too difficult to implement aside from the editor additions.