Can we take one city, maybe Den, and try an experiment that might create bonds between players?
TC in Den could be PvE, where players fight against invasions of mutants (or ants or aliens etc). Any players can show up to assist the players fight the NPC invaders. Targeting other players disabled. If the players win, any faction represented by 5 or more characters gets the benefits. It lasts until next invasion, announced at top of screen to all players (like TC did last year).