First: Hello owned! This is my first post here and i will try to make a good impression 
This is LUA- based door system which has these features
You can spawn door anywhere, but you need to edit LUA script (specificly gobject spawn coordinates, find those ingame)
You can spawn door levers anywhere, dont need to change anything!
There is only 1 LUA script which you need to modify to add aditional doors.
You need to make new door gameobject and item in SQL for every aditional door.
Script is not rly big, so i will post in here.
Code:
function lever_OnUse(pGO, event, player)
--first door
if player:GetItemCount(48907) > 0 then
pGO:Activate()
player:GetGameObjectNearestCoords(-14409.196, 415.022, 22.715, 150138):Activate()
player:SendAreaTriggerMessage("Welcome!")
--second door
if player:GetItemCount(48908) > 0 then
pGO:Activate()
player:GetGameObjectNearestCoords(-14448, 457, 15.421, 150138):Activate()
player:SendAreaTriggerMessage("Welcome!")
--dont change below if u need more doors.
else
player:SendAreaTriggerMessage("Ask owner to open the door for you!")
end
end
RegisterGameObjectEvent(17156, 4, "lever_OnUse")
OK LUA EXPLANATION.
GREEN: ITEM REQ FOR OPENING
RED: LEVER OBJECT (dont modify those)
BLUE: COORDS (first number is x, second y, third z, and fourth is door gameobject entry id (do not edit door gobject ids,thats fourth number, you can use same object, just modify coords)
Ok sql entriest now 
1. You already have door lever, you dont need to mod (id is 17156)
2. You need item for opening. Create them yourself and edit GREEN in script to your item ID.
3. Ok doors are must have. I was testing for about 3 days to find which will open on .gobject activate and i found ones, i changed they model so everyone can see opening of the same (looking like bar door, still you need to implement in SQL).
I will not paste sql here. I will teach u to make it manually.
Open SQL with editor, and look for entry ID 150137.
Duplicate that row, and set ID to 150138.
Set display ID to 2751.
You are done!
Thanks for reading, hope you like it 
This is my first post so dont be so strong at me
Cheers