As a big enthusiast of tabletop games, I have to say this definitely felt like one for me, and I love it! It is cool to see that a tabletop feel is what the developers were striving for and not just a pleasant coincidence.
Anyway, a few simple UI suggestions:
-When I make a pact with another player, please show their minimap units in another color besides red. I rely on the minimap to see when enemies have entered my territory, it would be nice to be able to see at a glance that the intruding unit is probably not a threat because it is my pact-ally. I'd also be able to distinguish between my pact-ally and people who are attacking my pact-ally, instead of just seeing a bunch of indistinguishable red dots in my pact-ally's territory.
-Fields need to be easier to see. Scrolling around examining the terrain is frustrating. If a mouse over the farmer hire button, or I select a farmer, please show the fields on the minimap, as well as some indication of whether it is being worked or not.
Some gameplay suggestions that may not be so simple:
-Immunity while being expelled is annoying. If my envoy is in danger and is in enemy territory, I can beeline for an opponent's town with an envoy in order to get expelled and thus save myself. Expulsion should only "protect" my unit once he gets back into my own borders (or maybe even not at all). At any rate, the invulnerability definitely should not kick in immediately. If I've been stalking that Envoy with my assassin and he just got himself expelled, I should have at least a few moments to finish the job before he is under protection.
-Immunity to Great Lords and heirs while delivering an offer of pact is kind of annoying, but I also see the need since the "target" house could easily kill the diplomat if they chose. What if the Great Lord or heir only had immunity against the other player while they were inside their borders (they must still be carrying a pact of course). If I want to stop Tully from killing my Great Lord, I can try sending a pact, but I would have to actually reach Tully territory before he becomes safe - it is not instant protection. Similiarly, once I reach Tully territory, I may still be vulnerable to some other House if they had units inside Tully territory.