O.K. Before we really begin the story. I'm going to clarify the ages of some of the characters. Of course all the adults remain the same age. The modifications are to the younger characters.
Mya Stone - 21
Theon Greyjoy - 20
Robb Stark - 16
Jon Snow - 16
Gendry Waters - 16
Joffrey Lannister - 15
Roland Baratheon - 14
Edric Storm - 14
Sansa Stark - 13
Myrcella Lannister - 12
Shireen Baratheon - 11
Arya Stark - 11
Bran Stark - 10
Tommen Lannister - 10
Rickon Stark - 6
Before I get started I will detail the military strength of each region in Westeros. I did my best to be accurate but I admit I shifted the numbers slightly.
The North = 40,000 men, 50 warships
The Iron Islands = 30,000 men, 700 ships (100 warships, 600 Longships)
The Riverlands = 50,000 men, 10 ships (2 warships, 8 Longships)
The Vale = 50,000 men, 70 Ships (30 Warships, 40 Vessels)
The Westerlands = 70,000 men, 100 ships
The Crownlands = 20,000 men, 200 ships (130 warships, 70 merchant vessels)
The Stormlands = 30,000 men
The Reach = 100,000 men, 1,300 ships. (300 warships, 1000 Merchant vessels)
Dorne = 20,000 men
I am going to include scenes from both the show and the books in this story. Due to the fact that I would be unable to tell this story by sticking to one single source.
P.S. this story was inspired by 'A song of some stuff being Different and some stuff being the Same', many thanks to Oursisthefury94.