Note that it is "Campaign Form" at the moment 
Heres my idea;
Journey To Atlantis
Interlude;
You see some military guys talking about atlantis. Then they spread out and go to different people and talk to them;
1. One military guy goes to a little house where John lives. John is a retired military guy. The military guy who comes asks him if he can come on one last mission, to find Atlantis. He comes with the military guy.
2. Another military guy goes to Eric. Eric is a scientist arkeologic guy. The military guys asks him if he can come on a mission, to find Atlantis. Also Eric comes with the military guy.
3. John and Eric comes to the military base and talks. A little while later they go to harbour with a little troop of marines. They leave the harbour with a little ship.
~End of Interlude~
Chapter One : Diving
1. You see a little cinematic where they leave the ship and enter a submarine. The submarine dives down under the surface.
2. Now you have to play. You first walk around and do stuff for the captain of the submarine, like fix a broken engine and stuff like that. After you finish those missions a cinematic starts.
3. Cinematic: A marine comes running in. "We spotted a large thing just beside our submarine. It cant be a whale or a submarine. Its much much to large for that! Its huge!" says the marine
The captian answers: "Enter you battle stations we need to fight this "thing" down!.
4. Now you have to use the submarine (the camera view is outside the submarine now, but all other just, not the monster, is still inside.). You have to kill the monster.
~End of Chapter One~
Chapther Two : Cave Entering
1. Starts with a little cinematic where you see that they have entered a underwater cave thats not ful with water. John talks to some people about the place their at.
2. Your mission is to bring your troops and the four trucks with stuff you've got. At least 2 of them must survive. This mission is like the one where you are Maiev and Tyrande and help Kael. Sometimes Kobolds and kobold like units will attack you from both behind and forward.
3. Somewhere in the middle of the way you come to a bridge. Some kobolds have placed explosives under the bridge. Now a cinematic starts;
"Im not sure we should go over that bridge." John says.
"Why not?" A marine answers. "Its the easiest way to come across the river."
"It doesnt feel good." John says.
"Look its totaly safe" Says the marine and runs over the bridge. But when he is at the middle of it the bridge explodes and you see some kobolds run away in the shallow water under the bridge. They are laughing.
"We must go around everything now. Hurry up!" Says John.
4. Cinematic ends and you continue to walk around everything and you meet some kobolds and kill them on the way.
5. You come to a cave exit and you set up a camp there, only for the night.
~End of Chapter Two~
Chapther Three : Atlantis
1. It starts with a cinematic where all the marine guys get out from the cave from the cave exit. When you come out you see an awsome view! You stand on a little cliff and theres a jungle-like enviorment. They see Atlantis now. John and all other guys just watch the great view over Atlantis.
2. You go into Atlantis and everything is quiet. A little bit too quiet. It switches over to a cinematic where you see John and all others walking on the creepy empty roads in atlantis. Suddenly alot of guys come out from everywhere and capture everyone.
3. The Atlantians take John to the Atlantian King. They talk a little, The king is angry and John explains that they are peacfull explorers. The king understands that they are peacfull and realeses them. But all marines, except John, the scientist and 2 other marines, starts killing all atlantians and takes the king as a prisoner.
The rest is up to you Feel free to remove, add and change/replace stuff!
or just an idea from your head 
