Ned took back with him the surviving Northmen, minus Robb's personal cavalry and retinue (the same bodyguards and friends he kept with him in canon). The bulk of Robb's forces are men of the Riverlands and Vale - specifically the relatively unbloodied Vale. The Stormlands, Reach, and Westerlands have suffered some overwhelming blows to their armies (and their pride). Attempting to raise more sizable hosts from them is possible but requires time unless you want to risk a famine in the middle of winter (which isn't caused by the Others here but is still looking to be a harsh one).
So ~3/8 of your men are Valemen, ~3/8 are Riverlanders and Stannis loyalists (Stormlands and Narrow Sea), and ~2/8 are the men you can keep from the defeated kingdoms without being viewed as unreasonable harsh for this season. You do have the option to send someone directly to the Iron Isles to see what's going on there - the departing fleet is not the only place Greyjoys can be found after all.
And those fractions are from the 80,000, I take it...
So 30,000 Valemen, About 15,000 Riverlanders and Stannis loyalists each. And 20,000 between the Westerlands, the Reach and Dorne, which is about 6,666 each.
So the 10,000 Westerlanders part isn't going to work. We could have them check out the Iron Islands, though.
I think having the defeated kingdoms participate in at least some capacity is a good chance for them to regain some pride. But have them do it acting as a part of the greater whole of the Seven Kingdoms. Defend the Realm and boost Royal Authority.
[] Plan: From Seven Kingdoms, One.
-[] The Seven Kingdoms will remain a united Realm. The previous victors can forgive, and those that fought against their rightful King, Stannis, before, can regain their honor and pride by fighting with their fellow Westerosi against those that would threaten them all.
-[] The relief force for the North and the Wall will consist of approximately:
5,000 men of the Riverlands under a lord recommended by Brynden Tully for his loyalty and military acumen.
10,00 Valemen the command of Bronze Yohn Royce for his loyalty and military acumen.
5,000 men of the Stormlands under a lord recommended by Davos Seaworth for his loyalty and military acumen.
2,000 men of the Reach under a lord recommended by Randyll Tarly for his loyalty and military acumen.
2,000 Dornishmen recommended by...Edric Dayne, I guess, for his loyalty and military acumen.
2,000 Westerlanders under a lord recommended by Tyrion Lannister, for his loyalty and military acumen.
Bronze Yohn Royce is to command the entire force. Have their lords order them to follow the Royce's commands until they reach North, and upon joining with your father or the Watch (whoever they contact first), follow Lord Stark's and/or work with the Northern forces and Lord Commander. There are reports of a huge wildling army coming to cross the Wall; their mission is to stop them. All the while, advise Royce to be wary of the Golden Company landing on the east coast and while the Iron Fleet has not reappeared, they could show up again any place or time.
-[] Send word to Tyrion Lannister. It's in the interest of everyone to investigate the Iron Islands and figure out just what the Ironborn are up to, and act accordingly from there. Lords Velaryon and Mallister will be sent to offer their direct assistance (and to make sure the Lannisters are playing ball).
The forces sent will include approximately:
1,000 Dornishmen.
2,000 Stormlanders
2,000 Riverlanders
1,000 Reachmen
1,000 Westerlanders
5,000 Valemen
The forces from each Realm will be commanded by a lord recommended by those you previously consulted. This will be under overall command of Tyrion Lannister. However, depending on how things go this can be diplomacy as much as it is a show of force. Keep that in mind if trying to talk to the Ironborn...though also keep in mind it would be Ironborn they'd they'd be talking to...
-[] The Hunt for Aegon:
Your remaining force will be held in reserve to deal with Aegon, or any surprise that comes to Westeros's shores in the meantime as he is being tracked down. This force is comprised of approximately:
25,000 Valemen
8,000 Riverlanders
8,000 Stormlanders
3,500 Dornishmen
3,500 Westerlanders
3,500 Reachmen
The forces from each Realm will be commanded by a lord recommended by those you previously consulted. Lord Tarly will be in command of the armies and Davos Seaworth in charge of the naval forces. Of course, you, Robert Stark II, will be in overall command. You cannot move your forces to chase after Aegon (or the Iron Fleet if necessary) until you know where they are. Send out 'trade envoys' to gather information on where Aegon is, or any word on the Iron Fleet for that matter. Consult the Manderlys, Lord Velaryon, Tyrion Lannister, for any contacts they have, trade related or otherwise. Desmera Redwyne would do well to prove her loyalty in a similar capacity. Tyene Sand said she would serve you however she could to get revenge against Aegon. Seek her and Arianne Martell's assistance in finding information on where Aegon is, and perhaps getting someone to poison him with any luck.
Maybe I'm being overly optimistic about mixing the forces. But I'm thinking Bronze Yohn Royce has enough of a martial repuation to command the respect of not only Robb's more loyal base, but any other troops sent. The same goes for Tarly. As for the Ironborn expedition...everybody can get behind kicking Ironborn ass.
But the mix is something I'm willing to rework. Right now it's 26,000 for the North/Wall, 12,000 for the Iron Islands, and 41,500 held in reserve.
Question though, should we send the Northern relief force by land or sea. By sea would be faster, and we could get them directly to Eastwatch by the Sea...but if the Wall collapses that could be bad.
If we go by sea, I guess have the Manderly fleet get them there?
Oh, the Vale, Riverlands, and Stormlanders...are those numbers for them also based on what they can afford to provide without hurting too much for the Winter,
@Charcolt? Do the numbers for the plan work as a whole?
As for Tyene, she is eager to help kill Aegon. And the Martells and Sand Snakes probably have contacts in Essos.
If we want to dedicate assets to defending the coasts, I'm not sure how many troops or naval assets that might take. We'd have to reduce the numbers for the other forces if we want sizeable defense forces just held in place. I kind of doubt it's necessary, though. The 'Aegon' force being held in reserve can be deployed elsewhere in case the Iron Fleet does suddenly show up.