Hi there here is my suggestion
We noticed that Regional materials are unbalanced , some are unavoidable for buildings ,and become very difficult to have due to the population... others are barelly useless ( central corn, flour... ).
It should be nice if each zones got 1 special tree 1 special heb 1 special ore,...
Which means it also should be nice if each material got an interresting purpose, to be sure that 1 tree from the zone x got the same value that a tree from the zone y
it will increase the trading system and the interaction between the servers.