The Players will be same color same everything. Except for a trigger which ALLOWS you to PICK UP weapons from dead bodies and such.
BackBone:
Your a soldier in a Regiment commanded by a Main Character [Computer]. You pretty much defend him and progress though the story. At one point you will stop and he will make a camp. Your next objective will be to eliminate all alien forces.
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How bout'? Good or what?

Needs to have more to it to be a worthwhile RPG. Picking up weapons has been done a million times so you need a better defining characteristic than that.

After some thought, I find that this is not very original. It seems to me that it's a classic zombie map with aliens instead of zombies. Only thing different is that you have to camp every now and then.

Also abilitys like: Grenade throwing, Vehicle/Turret mounting, Entering buildings, Ammo/Clips, Etc.

Much better than most maps. Making the main character a computer with triggered AI is a good idea.

There's also like terrain-wise areas i.e Towers.

Needs more plot...
And about the plot, you should start with weaker weapons, so that picking up new weapons would actually be worthwhile. Starting out as a soldier in a regiment, you would logically start out with a better weapon than most random dead bodies would carry.

My suggestion, for a generic zombie storyline:
You start out as a guy in a pub, (everybody seems to like the idea that you can get drunk in games, why else is GTA popular?) when suddenly zombies appear outside. It would need to be a relatively better into than I have mentioned, but that is aside from the point. Anyway, you form a group of people in the bar, all of whom start out with simple stuff like pool ques, and the bartender gets a shotgun. Your group forms the plan that the city is not a safe place to stay, and decide (after zombies start breaking into the bar) to exit the back entrance, and escape to the countryside. Along the way, one member of the group makes the suggestion that maybe a radio communication is being sent out for surviving groups. So the group runs into a store, turns on a radio, and several members go crazy. You then realize that the "zombies" aren't really the undead, but are created by listening to some subsonic message in the radio transmission. With only a few people left, they decide that the only way to save anyone else, would be to raid the local radio tower, and broadcast a new message. yada-yada-yada
It's still pretty generic, but an rpg needs a plot. One cannot simply say Aliens, and have that explain everything.

The plot relates nothing to zombies. Everyone will start with like a simple SMG and find beneficial weapons.

Make the RPG and prove everyone wrong. RPGs with minimal stories suck. Even Open RPGs have stories.

Okay guys, My RPG is more futuristic-like than any lame old zombie game. It will provide a series of mini-plots and a main plot, Got it?