So how does one design a NES to accommodate as many of these motivations as possible? What are the play elements that feed the "I want to play!" enthusiasm for each?
You are making the assumption that more players=better NES. Is it possible that better NESes are ones where there is a smaller player base which allows for more quality control (now granted this hold more argument to those who view NESes as more social activities; those who view it as more individualistic would care less about the quality of other players)? Is it possible that it would be better to design a NES with a specific target audience and build up the NES to meet that target audience rather than try to please everyone all of the time? Would it be preferable to nail one area and not do so well in other areas or to be just average in every area? Would it be a better NES to have a small, extremely loyal and enthusiastic player base, or a large player base made up of a few enthusiastic players but mainly apathetic or minimally interested players? As the saying goes, chase two rabbits, catch none. That is not to say that there wont be overlap, but should it be incidental overlap, so that if other people find something to enjoy, great, but if not, thats fine, or deliberate overlap, where things are deliberately changed (perhaps to the chagrin of other players) in order to chase after player numbers.
But if someone would like to create a NES that strives to make everyone play in it (and I certainly wont stop you), here are some of what I
think cause certain people to enjoy certain NESes.
Why Id Want to Play
Creator: I want to play in a NES where I control the destiny of my own country. The more freedom I have to create and shape my country, the happier I am. The focus of the NES should be on me the player, my stories, my orders, my vision for the country. NESes are the players game, not the moderators. So if you want to design a game that makes me happy, you need to design a game that gives me freedom: freedom to create the culture (no pre-made culture for me!), freedom to shape the country, freedom to determine its political, economic, and religious institutions. The more you limit my freedom of action, the less interested I am in your NES.
Goal-Orientated: I want to play in a NES that gives me a challenge and the most important characteristic of a moderator is giving me those challenges.. It is no fun when I set goals if they are too easy to reach. At the same time, I dont want the moderator to make my goals impossible to reach. If I set a goal to unite Italy, dont let me just steamroll through NPCs so that I dont even need thought or skill to achieve my goals, make them hard enough that I have to come up with a good, or even great plan to succeed. The NES also has to be consistent enough that I know that if I do X I will achieve Y. If I come up with a great plan that would work only to see it fail for some lame reason, I will be extremely mad. On the other hand, if I fail because I failed to take something into account in my plan, or for some believable reason that I can accept when it is pointed out to me, instead of being mad, I will just be more resolved to achieve my goal.
Immersionist: I want to play in a NES where the characters speak to me. If I dont find an interesting character, or an interesting setting to make an interesting character, I am not interested. I want to be able to roleplay a character so that I can immerse myself in the NES, anything that destroys that immersion (unrealistic actions, bad spelling in official diplomacy, an inconsistent world) limits my enjoyment. The most important characteristic of a moderator is creating and maintaining a believable setting. By maintaining a believable setting, the moderator should referee between players, and in certain cases, overrule player actions that dont serve to create a believable setting. I can play in either rule heavy or rule light NESes, the important thing is that there is a standard of believability and something, either rules, moderators, or other players enforce the standard. Also, whatever that restrictions there are in the NES, such as rules, must have a in-world explanation for them: rules are a certain way because of playability, fine, but give me a reason I can view that rule within the context of the world (for example if every nation starts out equal in everything to make it fair, I need to know
why every country in the world is equal from an in-game perspective).
Gamer: I want to play in a NES where I am challenged by other players. The moderator needs to be able to resolve player conflicts (whether in political, economic, religious, sphere) in a consistent manner. Complicated NESes are fun, as there are more opportunities for my skill to shine, but simple NESes can be fun as well, it really depends on the other players. I find it fun when I am interacting with other people, building up alliances through diplomacy, engaging in a technology race with my rival, destroying my enemies in war. NESes where I am not surrounded by players (such as early on in fresh starts) are boring. Settings where I am not allowed to compete against other players (such as when the NES is dominated by one power and we all have to do what they want) are boring. The most important characteristic of a moderator is being unbiased, dont baby other players, if they arent as good as me they deserve to lose.