Nice improvements to diplomacy, thanks. I want to suggest that vassals and PU nations should be surrounded with color of their masters in political map:
I think this is a good idea, though I'd prefer if the colour is only around the outhermost borders and not the mutual internal borders, so in this case no red line between SWE and NOR, no brownish yellow between HUN and TRA etc. but only the borders they share with countries that do not have the same overlord