So, I've been using the nation browser for a ground campaign, and it definitely works, but it's a little...simple, I suppose, would be a good word for it. A filtering system would make going through it a lot more convenient, and here's some potential ones off the top of my head:
-Last Active since X (so you can filter out all of the Abandonias and vacationers)
-Has X Resource (so you can see at a glance what nations have, say, Oil, if you're in need of it)
-In/Not in Alliance (For recruitment and raiding purposes)
-Within X and Y score range (for stalking war targets or finding rough equal nations)
-Not X Color (this one's just for war purposes though)
So on, so forth. Not deal-breaking without, but it'd just be a nice thing to have. Maybe not with these EXACT options, but something like that.