posible to mod river=road for trade?

[flimo]

title pretty much says it
im thinking this could help a few of the minors to get trade with higher civ countries
atleast after the higher civ countries colonize a bit
and in those times rivers where indeed major trade routes

 

[Sute]{h]

I'd say the easiest way of doing this would be adding a road to every river province in the history files. Someone might have a better solution though.

 

[Featauril]

You could create a new building that would be unbuildable, called "river trade", and add it to river provinces. This advance would have the same properties as roads.