With the current player base being [i hate to use this word] small, to facilitate RP, players should be almost herded together. The heat map does that. If they could pick any city to be in, having 5-10 players in each major city would make it harder to meet and interact with new players.
Sure, later when there are more developments, and more players, having basic trainers would be good... but for now, I still think the heat map is a good idea.