It would be amazing but if your talking about the signup thing it would have to be in a different server and it would kinda kill the idea of a giant war. but say at a set time on a set day this was set to start the war for 2 hours or such and all players participate. only problem with this are towers guilds complaining. I have to say that guilds would be one of the best parts though. Using your guilds specialty and combat friendship and forming squads and going off and doing your own thing. I currently things called paintball scenarios and its about once a year and it reminds me of your idea. We camp out then play a whole game nonstop 10AM until 11PM. We have generals who sit at our base and when we have to respawn they will send the majority of people who are loners to go do some 1 on 1 noob war, while tournament teams and woodsball teams are usually chosen to do the special, offside stuff to get some props and such.
The only real thing i can add to your aweeeeesome idea is a lets say the teams are (Red v Blue). Their are a few admins and well known people who take "General Rules" and they cant broadcast to their color team to certain objectives. They also send well numbered guilds to do some specially hard stuff. Sound like the funnest thing anyone could do with a guild.
Also i think teh prize shouldnt be 1k. that would be very generous from stephan and xor and such noting alot of players would just afk or somthing and they could get 1k easy. Prize for winning should be like wavable flags as a gani, a trophy, or/and a hat. mabye some holiday tokenss?
In order to add some cool, increasing gameplay stuff, i think the game should have many objectives. Broadcast messages from your team could keep players spread out,
a few missions that generals are told their are burried items in a certain zone and whichever team digs it up, and then carries it (like a bush/bomb) back to the base.
One where each of the generals choose on of their best sparrers and they have a tournament and winner will get teh team bonus points,
Constant tower ownage will give each team X-number of towers held bonus points. This should last the whole game.
Regular broadcast missions such as holding a flag in burger refugee like some awesome KOTH,
Team with more PKs by the end get more points.
Oh and respawn for players should be like 6 minutes, then -1 minute for each tower your team holds