I think the best set of chat channels should be as follows:
Help chat - Available indefinitely while the character is on Haven, once on the mainland it is on a 72-hour in-game timer. After that, the character is removed from it forever.
Local town chat - Available to all within a radius of the town that covers the town area plus the outskirts. Those who are citizens of a town will have a [Citizen] tag next to their name.
Proximity chat - What we have now, essentially local chat that can be heard within a short radius of the player talking.
Proximity yell - Same as what we have now as yell, has a larger radius than proximity chat.
Guild chat - The general chat exclusively available to members of a guild everywhere on the map.
No wilderness chat. Out there, no one can hear you scream. Except maybe the Predator.