The game needs scenarios and since ASOIAF has a rich history it would be easy. Here is an example how this game could work within a scenario:
Robert Baratheon has just called on his bannermen to revolt against King Aerys II knowing he has Ned's and Jon's backing. There is news of the Tullys joining the cause too.
Game starts from here and each player is situated on Westeros' map in correspondence to their first pick. Each turn takes two weeks which means a maximum total of 48 moves for this scenario.
The scenario has three different phases with a maximum of 16 turns per phase save for the third.
Phase I: Recon (AGOT)
During this phase players should use their scouts and assassins for reconnaissance and crippling the opponents. Players also get to move their armies during this phase or choose to improve them via recruitment/advanced training or weapons upgrade. Another option is to upgrade one's castle and fortify defenses.
Players also get to send envoys/ravens to plot new alliances or struck right of passage deals etc.
Players do not have the option to attack another kingdom during this phase but their armies can move freely unless exposed by an enemy's scout. In case of discovery the particular army will receive a -30% strength penalty and vulnerable to an attack from the army that which the scout owes allegiance to the next turn as long as the defending army is situated somewhere within their own territory. The -30% penalty will be active unless the scout is killed/moved or the affected army moves out of the hostile territory into a friendly one.
Phase II: Fog of War (ASOS)
The time for covert affairs is over and players get to attack their enemies and conquer their kingdoms. This phase will feature the mandatory battle of Summerhall where Robert has to defend Storm's end from loyalist forces. This is a decisive battle whose end determines the course of the game since in case of Robert's defeat he will die and his army will perish completely leaving the rest of rebel forces in disarray and alone (morale hit). In case of a rebel win the Storm's end army receives a 10% upgrade in all values and its castle will be rendered invulnerable.
The loyalist forces have three turns to reach the Stormlands or the battle will be forfeited in favor of the rebels. Apart from this main battle the rest of the phase will be up to the players to fight it out.
Phase III: The Reckoning
This phase features another decisive battle "Battle of the Trident". Both rebel forces and loyalists have three turns within this phase to reach the trident and battle it out. The victors will gain a +20% morale boost and shall not face opposition on their way to either King's Landing or Storm's End. This phase is consisted of only 8 turns which means if the victors do not manage to reach KL/SE in time and conquer them Westeros will succumb to chaos.
1- Draft does not need to change much just some modifications to accommodate the changes due to the setting.
2- I'm introducing concepts of stand alone armies for each house based on my own calculations and numerous discussions on the issue and a bit of balancing the numbers to suit the game.
Winterfell: 60000. 4 to 1 foot to cavalry but lacking a fleet.
Pyke: 35000 foot soldiers all sea warriors with 500 longships including a number of bigass 100+ oar battleships.
Riverrun: 45000. 3-1 foot to cavalry, limited scout ships (boats).
Eyrie: 45000. 3-1 foot to cavalry, limited fleet situated in Gulltown.
Casterly Rock: 60 000. 2-1 foot to cavalry, a fleet of 50-60 larger ships and some longships.
The Reach: 70000. 3-1 foot to cavalry, a fleet of 200 ships with 100 oars or more
Stormlands: 30000, 4-1 foot to cavalry, no fleet badass castles.
Dorne: 30000. 2-1 foot to cavalry, limited fleet.
3- Morale and Mobility: In addition to A/D I suggest adding the two values to account for assassinations, news of defeat, friendly/hostile terrain, foot to cavalry ratio and such. Morale boosts or hits impact the A/D/Mobility of the whole army, Robert's death in Summerhall would mean a morale hit of -50% on the rebel armies for three turns e.g.
Mobility rules: An army within a city requires one turn to prepare to march, all armies are located within the castle capital of the region by default at the beginning. After that it takes one turn to reach any location within one's own territory and another turn to enter an alien region.
When in hostile territory or stealth mode, armies take two turns to reach a city/town or 4 runs to reach the capital of a hostile house.
Mobility value is based on 100% foot which means the above is subject to change based on the army's foot to cavalry ratio.
The game will need a moderator/all seeing eye/God/Yo Daddy! which I will be glad to for the first time. Feel free to ask/comment/recommend since beyond this point it needs second opinions and tests to develop.