Heathen hofs
One thing I really feel is missing from this DLC is Heathen hofs in Denmark and Norway. Pagans should have a few of these around in their homeland. Basically a few remote Pagan places of worship that a player can travel to to participate in blót rituals or other sacrifices. These could also act as locations where Pagan Priest and Berserkers (Odin's special warriors) can be recruited from. This would imo really add lot of immersion for Viking players and give them a very good reason to travel back to Norway and Denmark. Not only would you be making sacrifices to the Gods, but you could recruit some awesome unique Pagan troops that you can get at the hofs.
Rituals
This doesn't have to be anything crazy, even just some dialog options would be fine like the Priest at the halls. Though it would be cool if there was a way to represent blót rituals and human sacrifices. It might even be pretty cool if you could drag a lord prisoner to one of the hofs and give them a blood eagle to kill the lord. This would come at a cost, but the option could be interesting.
Odin's Warriors
These would also be a place where the true warriors of Odin gathered and could be recruited, though they should be expensive they would add a nice element to any viking army.
Pagan Priest - The hofs would offer a static location to recruit them from to guide your men in the pagan ways.
Berserkr - This is one unit I want to see in the game more than anything, they where very real and there is all kinds of information about them littered throughout the sagas. Apparently King Harald Fairhair used Berserker bands as his shock troops and where sometimes ranked as high as royal bodyguard.
Haraldskvæði saga describes Harald's berserkir:
I'll ask of the berserks, you tasters of blood,
Those intrepid heroes, how are they treated,
Those who wade out into battle?
Wolf-skinned they are called. In battle
They bear bloody shields.
Red with blood are their weapons when they come to fight.
They form a closed group.
The prince in his wisdom puts trust in such men
Who hack through enemy shields.
The Icelandic historian and poet Snorri Sturluson (1179–1241) wrote the following description of berserkers in his Ynglinga saga:
His (Odin's) men rushed forwards without armour, were as mad as dogs or wolves, bit their shields, and were strong as bears or wild oxen, and killed people at a blow, but neither fire nor iron told upon them. This was called Berserkergang.
Berserkr would be an easy unit to do since there is a lot of description of them and what they would wear into battle. They could have a mix of wolf and bear pelts with a few helmets in the mix, shields, swords, and one and maybe even two handed axes. I would definitely give them give them a 10 in power strike and maybe even consider making them have a higher athletic skill to represent them being furious. Basically a fast and powerful shock troop that would melt away in a prolonged melee.
Wolf pelt model
Bear pelt + pants model
Anyways I know this is mostly wishful thinking, but I think it could be pretty awesome for this content.