I do not see the market line as "broken". It just forces the player to plan ahead and not to develop every single province into a citadel. Your first point in the conclusions is faulty too. You should develop markets to the max in 5 provinces (preferrably ones with high value trade goods especially gold and ninja specialization provinces; preferably the ones you have early in the game so that the extra concentrated economic growth really kicks in over the course of the game). The reason for the 5 maximized market line provinces is that those will be the ones where you station your trained up Metsuke. High level metsuke tax boost is enormous. Playing on VH, in the later mid-game, my concentrated growth provinces tend to have value close and above 10K (and growing fast). Metsukes tax the hell out of these provinces (50-70% tax rate). Meanwhile, at that stage I have many level 1 provinces with maxed out farms, giving me some 30-40 extra food for overall growth.
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