Siege upkeep

Yeah I agree. basically this type of system would greatly increase the strategy involved in the game, and mean that even very small players can have considerable impact on a war simply by placing a blockading army half way between a town and destination. And hope the player doesn't notice untill too late.
However i realise before all this could be implemented the full function of messenger units would need to be implemented as well as the ability to provide an escort for caravans. otherwise 1 commander and 1 troop could be placed on multiple squares and take forever to clear. when realistically you should be able to go from blockade to blockade rather than go back to town each time.