Re: Kingdom building/management systems
Having tried to run a Birthright game, I'm going to weigh in here:
Birthright has some good aspects running for it: It's got a good amount of supporting information for it. You've got books about regions, cultures, campaigns, adventures, and so on. It does a very good job of putting names and faces and numbers into place for having a setting that can just kind of exist as written.
The downsides, however, shoot it in the foot. One downside, depending on your fancy, is that it's all second edition ADND. And while there's a fan site that has forums, and pdfs, and a fan conversion to 3.5 (and maybe even pathfinder now), the bulk of the material is still 2nd edition. If second edition is not your cup of tea, this is a downside.
An actual downside, however, is that if you want to run it using the rules as written, with the npcs as they've been set up and so on, and do a reasonable job of keeping real track of what the not player run kingdoms are up to, then you will need a spread sheet. And maybe to use the custom program that is on the birthright fan site I mentioned, and maybe to make a program of your own to do it, because I know the one that is on that site (at least when I tried using it) didn't really have the Rjuvik area filled in (or whatever it's called, the viking area with badasses and their axe wielding culture of kicking ass and having a giant wall to fight invading goblinoids off of).
Another benefit however, is that you've got a war system in place, you've got an economic system, and you have the sweet sweet system where the power of the land is tied to ruling it, the whole bloodline system and all it's glorious implications. Of course, you probably shouldn't worry about balancing the players too much, because some of them might wind up with things like Regeneration from their bloodline, or the power to call elementals once a week. It's got a good, flavorful setting. And with the whole 'need a bloodline or to be elf or half elf' to cast strong spells helps ensure that the players can feel powerful when their wizard drops a fireball, since it's just not at all the kind of common spell that it winds up being in other settings.
So, if you're looking for a system that can do a lot? Birthright will see you through...it just might take a lot of book work (which is the main reason I stopped running my birthright game, too much book work to run the other countries)