Massive muliplayer, there are several cities, players can travel to these cities and perform services. This is a very small part of the game, I need it very simple. It does not need to be playable on its own and all the time, it is just an extra (I basicly want to be able to introduce some rare professions, like minstrel, which don't fit with the core game mechanic too well).

For example there is a minstrel that travel across cities and can sing in cities to earn money.

Example solution:
Each city gets +5 demand per hour (depending on city size, could be +20 for bigger ones, also the demand is multiplied by number of players). Then any minstrel can perform in that city, which decreases the demand by -1 and the minstrel gets paid 1 gold per current demand. So, if the city has accumulated 100 demand and he performs once the demand is lowered to 99 and he gets paid 99 gold (so the more the demand is satisfied the lower is the payment, which makes it self balancing and promotes visiting all cities evenly).


Any problems with this I don't see? Any better (or simplier ) solution?