Yes Troy, we DO need a trade republic system. I always felt that Merchant Republics got short shrift - they lose several key diplomatic options that make them far less fun to play. My goal was to make England into a trading master, then overthrow the monarchy for a Calvinist Trade Republic (perhaps not 100% realistic, but Oliver Cromwell is CLOSE). But I never wanted to, not only because the stability hit, but also because - once done, I would have no diplomatic options. Hopefully these changes will address that.
I'm excited and apprehensive about the dynastic system as well. I hope that it finally allows EUIII to properly simulate the dynastic squabbles that characterize the Early Modern Era (i.e. War of Spanish Succession). Without historical events, it was difficult to create these. I agree, In Nomine was a big step forward - easily, as you said, the best expansion I have seen. But still, some things needed to advance, and the dynastic system was one of them.
However... I fear that the overly complicated Crusader Kings model will rear it's ugly head, lead to performance issues, crashes, and more emphasis on who people are marrying at the expense of the 100 other things you need to think about in EUIII. Hopefully this won't happen.
I agree regarding the CB system - it looks fantastic!