It's impossible to set rules for role play, because there are trillions of possibilities. Archers vs archers? Mine are on higher grounds and have long bows, better range, I get first attack.
Generally common sense is the rule, and that's really as far as people can go without making up rules that take 10 lines of text "no more than x vehicles unless y or z condition occurs, in which case you can have x vehicles but not on Tuesdays not Thursdays, an each vehicle can only carry g people unless condition q is met..."
It's just not worth the effort. There are stupid players. It's just a fact of life. You go on a TDM? Team killers. Zombie team defence game? They lock you out of the safe house. Spaceship build? They make a square room and make the whole thing glow and call it a super mega cannon death room of win.
If an admin believes your not playing by the rules because you refuse to play with someone, then your clearly not presenting WHY your not playing with them.
Take for example, the last mini empires I hosted.
Person x wanted to ally with me and set up a small colony on my 128x128 custom island. Person y said he wanted too as well since person x could, but person y only wanted three things; my favor, better way to attack person x, and more land. I turned him down, and when he insisted, I had person x wage war on him. If person y tried to meta-game with him 16x16 island, I would D-wand half of his fleet as punishment.
Make of it what you wish, but metagaming and stuffty mini empires aren't gonna leave anytime soon