You could always have to warn the game 10 turns before your DoW that you are going to attack, just like the "wait 10 turns and DoW deal". I was sure it would be in GnK before release.
Now that I think of it it might have been just cumbersome and annoying...
Warning the game turn turns before you attack... that would create some annoying situations, for example:
1. Another player's army shows up on your doorstep and starts positioning their units for war, and you can't even strike at them until they DoW you first because they already told the game 10 turns ago and you didn't.
2. If you have an ally that is attacked (and defensive pact tech not discovered yet) you can not help your ally for 10 turns.
3. You have a worker captured by a barb, and just before you can rescue it, another player takes it instead. You cannot kill their unit and take your worker back, because you would have to wait 10 turns for DoW.
4. At the beginning of the game, you can use a few cheap units (scouts) to block other player's settler, have a unit on the city spot, and then settle the city in their face while they can do nothing about it.
5. Another player can pillage your trade routes (road not in their territory) and sit their scouts there for 10 turns while you bleed gold (and happiness if you have liberty.)
6. Neighbor builds Manhattan Project. Guess what, you will get nuked, and you can't even attack first for 10 turns.
7. Player builds Apollo, UN or the cultural victory project. Game is over in 10 turns you can't even try to stop them.
I am sure there are many other ways to exploit this, these are just some slimy things that I would do.
