Right now, the most concrete information about Assassin's Creed Ragnarok is that it likely revolves around vikings, but there are plenty of rumors on how it'll bring back features, introduce new ones, feature an inconsequential male or female protagonist choice, have a map focused on England and Scandinavia, and so much more. It is changes and forward momentum in design that has led to the resurgence of the franchise, but sometimes, the best way to go forward is to look back.
Many want to see Assassin's Creed Ragnarok return to form in a manner similar to the older action-adventure games, but that's not likely to happen. However, that's not to say that aren't lessons to be learned or "compromises" to be made, and there's a gameplay feature in Assassin's Creed 2 (as well as others) that would bridge these differences well.
Assassin's Creed 2 Gameplay Progression, Leonardo da Vinci
In the classic Assassin's Creed 2, Ezio is a fledgling Assassin, new to the Brotherhood and seeking revenge for the murder of his family. He's new to the world itself, still pompous and proud, and a far cry from the wise Ezio who retires at the end of Revelations. He may not have made it so far if it weren't for his dear friend Leonardo da Vinci, who repaired his Hidden Blade and constantly updated his abilities. This natural gameplay progression is something that the new game should mold into itself: natural progression.
Instead of being given every tool from the get-go and simply improving them via Skill Trees, perhaps the game could slowly introduce new gameplay mechanics throughout. Leonardo da Vinci, for example, gave Ezio a second hidden blade—something revolution for the time. But he also introduced the poison blade, hidden gun, reinforced gloves for climbing, and so much more. There were even temporary inventions like the Flying Machine and the enemy War Machines that played a role in Assassin's Creed Brotherhood. What these unlocks did, as some require Ezio to find Codex Pages, was varied the gameplay across the game and introduced new mechanics to vary up some missions later on as well.
Assassin's Creed Ragnarok Gameplay: Berserker Abilities
One way this could be implemented is through the rumored Berserker abilities. Befitting a viking, there's reportedly a gameplay mechanic that sees the player become enraged, swapping up stealthy gameplay for a powerful damage-dealing burst of power, that could be modified with runes that change the element of this (at the very least). Unlocking glyphs to unlock new Berserker abilities would be a start, especially if it transcended beyond simple element changes. Perhaps one Berserker ability was a simple enraged player with a flaming axe, while another could see the player become like Thor wielding Mjolnir(a leaked item for AC: Ragnarok's special edition).
At the same time, there's a lot of more natural and realistic elements that could take on this progression. While Viking weaponry wasn't nearly as advanced as those of the Renaissance, these weapons could still be changed and upgraded like Ezio Auditore's. It wouldn't be hard to explain in a world where the First Civilization existed to showcase improved weapons like a poisoned hidden blade, a hidden ranged attack, or even something as insane as a flying machine in a world where the Isu show themselves to be gods.
Of course, there's no telling hat the finished Assassin's Creed Ragnarok will look like, so fans just need to simply wait for Ubisoft to show its hand.
Assassin's Creed Ragnarok is rumored to be in development.