One lesser discussed thing that I think could be super important is the fact that we likely/potentially will have an undead Jon Snow leading a wildling army.

I ride to Winterfell alone, unless …" Jon paused. "… is there any man here who will come stand with me?"

The roar was all he could have hoped for, the tumult so loud that the two old shields tumbled from the walls. Soren Shieldbreaker was on his feet, the Wanderer as well. Toregg the Tall, Brogg, Harle the Huntsman and Harle the Handsome both, Ygon Oldfather, Blind Doss, even the Great Walrus. I have my swords, thought Jon Snow, and we are coming for you, Bastard.

UnJon & his Wildling Army

At the end of A Dance with Dragons, Jon Snow decides instead of going to Hardhome that he will instead be marching south to fight Ramsay Snow/Bolton (Pink Letter).

Unlike Stannis who made the Free Folk kneel and never really made them his:

It is too cold for this mummer's show, thought Jon. "The free folk despise kneelers," he had warned Stannis. "Let them keep their pride, and they will love you better." His Grace would not listen. He said, "It is swords I need from them, not kisses." -ADWD, Jon III

and since the wildlings follow strength, we should look at how they treat Jon since he doesn't make them kneel:

That goes for all of you. I will never ask you to kneel to me, but I will set captains over you, and serjeants who will tell you when to rise and when to sleep, where to eat, when to drink, what to wear, when to draw your swords and loose your arrows. -ADWD, Jon V

we should look at how the treat Jon:

And then Halleck. "I don't like you, crow," he growled, "but I never liked the Mance neither, no more'n my sister did. Still, we fought for him. Why not fight for you?"

and:

The dam broke then. Halleck was a man of note. Mance was not wrong. "Free folk don't follow names, or little cloth animals sewn on a tunic," the King-Beyond-the-Wall had told him. "They won't dance for coins, they don't care how you style yourself or what that chain of office means or who your grandsire was. They follow strength. They follow the man."

Then we see numerous wildling chieftans swear themselves to Jon:

Halleck's cousins followed Halleck, then one of Harma's banner-bearers, then men who'd fought with her, then others who had heard tales of their prowess. Greybeards and green boys, fighting men in their prime, wounded men and cripples, a good score of spearwives, even three Hornfoot men. -ADWD, Jon V

and:

Amongst the stream of warriors were the fathers of many of Jon's hostages. Some stared with cold dead eyes as they went by, fingering their sword hilts. Others smiled at him like long-lost kin, though a few of those smiles discomfited Jon Snow more than any glare. None knelt, but many gave him their oaths. "What Tormund swore, I swear," declared black-haired Brogg, a man of few words. Soren Shieldbreaker bowed his head an inch and growled, "Soren's axe is yours, Jon Snow, if ever you have need of such." Red-bearded Gerrick Kingsblood brought three daughters. "They will make fine wives, and give their husbands strong sons of royal blood," he boasted. "Like their father, they are descended from Raymun Redbeard, who was King-Beyond-the-Wall." -ADWD, Jon XII

Howd Wanderer swore his oath upon his sword, as nicked and pitted a piece of iron as Jon had ever seen. Devyn Sealskinner presented him with a sealskin hat, Harle the Huntsman with a bear-claw necklace. The warrior witch Morna removed her weirwood mask just long enough to kiss his gloved hand and swear to be his man or his woman, whichever he preferred. And on and on and on.

And while its possible that with Mance still alive some of them might revert to him, but as I have pointed out above they follow the strong and Mance has been defeated.

So right before Jon's death the wildlings agree to follow him south to battle Ramsay:

Yarwyck and Marsh were slipping out, he saw, and all their men behind them. It made no matter. He did not need them now. He did not want them. No man can ever say I made my brothers break their vows. If this is oathbreaking, the crime is mine and mine alone. Then Tormund was pounding him on the back, all gap-toothed grin from ear to ear. "Well spoken, crow. Now bring out the mead! Make them yours and get them drunk, that's how it's done. We'll make a wildling o' you yet, boy. Har!"

"I will send for ale," Jon said, distracted. Melisandre was gone, he realized, and so were the queen's knights. I should have gone to Selyse first. She has the right to know her lord is dead. "You must excuse me. I'll leave you to get them drunk."

"Har! A task I'm well suited for, crow. On your way!"

But I wanted to look at few things that are pretty big with regards to an undead Jon Snow and his wildling army.

Reaction of the Seven Kingdoms

Cersei has already been plotting to have Jon Snow killed, what is going to happen when rumors start to leak out that Jon Snow was assassinated but resurrected and is marching south.

Keep in mind that there won't be any confusion as to his identity due to Ghost, but people may claim he was never actually killed.

The Seven Kingdoms and primarily the North are not going to be cool with wildlings marching over their lands:

"Lord Snow," said The Norrey, "where do you mean to put these wildlings o' yours? Not on my lands, I hope."

"Aye," declared Old Flint. "You want them in the Gift, that's your folly, but see they don't wander off or I'll send you back their heads. Winter is nigh, I want no more mouths to feed." -ADWD, Jon XI

Its possible that due to all of all the competing factions in the north that some contention could lie ahead: War of the Wolves II

Ramsay

Characters who die tend to become focused on what their purpose or job was right before they died (Beric, LSH, etc.), with that in mind Jon may become obsessed with fighting Ramsay.

If interested: Will the Battle of the Bastards Occur in THE WINDS OF WINTER?: An Analysis by u/bryndenBFish

The Stark Direwolves vs. Ramsay's Hounds

Fighting Skill: Jon Snow vs. Ramsay Snow

Night's King 2.0

While not a direct comparison an undead warrior leading an army from beyond the wall does parallel the Night's King. Its an interesting thought just due to the fact that we know that The Winds of Winter is going to be a super dark book, and that Bran & Jon were originally setup as bitter enemies.

Other Notes

Jon has set up wildlings in numerous of the abandoned castles along the way:

All In All, It's Just Another Castle on the Wall

These quotes about Borroq could hold some meaning for unJon and his army:

And so long as Borroq and his boar are about, I dare not let him loose." The skinchanger was to accompany Soren Shieldbreaker to Stonedoor once the wayns carrying the Sealskinner's clan to Greenguard returned. Until such time, Borroq had taken up residence in one of the ancient tombs beside the castle lichyard. The company of men long dead seemed to suit him better than that of the living, and his boar seemed happy rooting amongst the graves, well away from other animals. "That thing is the size of a bull, with tusks as long as swords. Ghost would go after him if he were loose, and one or both of them would not survive the meeting."

and:

As for Borroq, Othell Yarwyck claimed the woods north of Stonedoor were full of wild boars. Who was to say the skinchanger would not make his own pig army?

TLDR: A resurrected Jon Snow will have a wildling army sworn to him. Its possible that his resurrection takes place so late in TWOW that there is no time to focus on playing the game of thrones, but if not his character status (undead) and army (Free Folk) is going to cause some serious contention in the Seven Kingdoms (primarily the north).