So, me and a GM friend of mine are creating a game.

The premise is that you have a character (3.5 ed. more or less), but you're also responsible for a whole nation. Starting off as an individual town/village and expanding and developing your nation into a superpower which competes with other nations.

However, we really haven't thought through the mechanics for improving the nation, and we'd like some help, should anyone have any suggestions.

the possible attributes of advancement are
Agriculture, Military, Philosophy, Politics, and Science.

there's no magic in this universe, but there are psionics.

You know, if you planned on using 3.5...you could try and adapt the rules to make each City/Nation be represented as a Character.

Have each ability score represent an aspect of the Town (Constitution equates to Economy, Intelligence equates to Technology), and your actions help to make the town "level up." In time, as borders expand, you can modify the Leadership Feat to include nearby and allied towns.

The advantage to this would be, so long as you are familiar with 3.5, the whole process would be intuitive.

I like the idea of settlements gaining experience

i should have clarified;

the current idea is essentially rolling a d20, and adding two of our characters own ability modifiers.
(ex; politics is cha/int and philosophy is int/wis)
dependent on the roll, the nation advances accordingly.
but i dont like that system as it feels somewhat uninvolved.

Hurray, my town leveled up!

What feat should I take? Public works or indoor plumbing...?

I recommend Greater Palace. You're the important one here!

Usually, linking characters to towns is just something like giving the level 6 party a keep, which they can pour money into to make better. Adding another dimension to that, and making the characters actually act as a mayor or king or prince or whatever really would just add diplomacy checks and maybe adding some elements of mass battle strategy.

Bump?

Azazel, can you PM me any notes you might have already? i can let my imagination run wild for a while, if you like

You might want to see if there's anything here that will help you: http://www.myth-weavers.com/wiki/index.php/FactionRPG

Try the book: Empire.