My guild (when it existed) got in a particularly nasty guild war with some guild called the Klyros Mercs or something (they were all Klyros, and they referred to themselves as "Mercenaries." I care less about the name, really). What I mean by nasty:
1) Bodies were falling everywhere. Both our guilds had around 30+ members online at one time, and no city, death realm, or respawn point was safe. It took a total of 20 kills to get from the 2nd-to-highest guild rank to the highest rank. It was supposed to be almost impossible, and yet we had 3 people get there, and a few more get close.
2) Insults were flying through the air. A few of the enemy guild members had a thing about making "yo mom" jokes and cussing us out after they died, thinking it was safe to keep them in brackets. I'm ok with RP insults like "YOU SON OF AN ULBER" and "GO TO THE DEATH REALM WHERE YOU BELONG" but when they change to "your moma's sword is longer than mine," then there's a problem.
3) There were no rules, people were actually hacking. It went on for like, a month, and both guilds started to lose members just to leave the guild war because it was so ridiculous. I think we got the Nexus of Devotion to join our side, and then the Mercs got some guild called "Princes of Blood" or something like that to help them.
We won, but it wasn't really fun. Both guilds had lost a ton of their members, and though it was glorious to win, both giving and taking insults and cheap shots at the enemy guild(s). It's a lot more fun if guilds war for RP purposes, and are clean and honorable. I would really prefer them to be bloody scraps where entire guilds are obliterated, but the fact that this is a game makes it all too competitive.
I like your rules. They would make it fun (although I don't like the whole 'if he calls himself a citizen, you can't attack him' rule; any guild that is in a guild war shouldn't have any peaceful civilians involved). The only problem would be making people follow it. I'm sure there's a ton of people out there, even in a game like Planeshift, who really don't care about conduct as long as they win.