I would like to apologize in advance if i'm requesting what has already being suggested, or what admins have already justified leaving out/adding in, and if any of this seems totally ridiculous. I agree with most of what has being mentioned, but in addition I would like to see..
Crouching - Would allow players (like in Vikingr) to take cover, to create more efficient formations (more depth to gameplay) and adds more immersion among other things.
Get rid of infinite ammo while on boats - Because that's incredibly annoying and immersion breaking.
Add certain items from Brytenwalda/remake them if you must - Sutton Hoo helmet (very expensive in multiplayer), throwing axes, long 2 handed axes, leather armour, seaxes unique to each faction, banners unique to each faction, things like this. Because in warband historical accuracy is important, but not to the extent where anything considered historically inaccurate is totally excluded, taking away from allot of potential fun. This issue has no doubt being discussed in detail else where on the forum.
Make the combat speed slower, make wearing armour slow you down, it feels like I am on a hover board in multiplayer and armour feels weightless. In my opinion Vikingr and other mods got it right with actually adding weight to the character, it makes combat allot more immersive, focused and incredibly entertaining, not where players are running by one another at incredible speeds.
End round music - On multiplayer and single player, when a round is won it should play a badass Viking victory song, when lost it should play a sad one.
Shield Bashing should also initiate a battle cry - It's hard for me to justify everything, you know, just more immersion.
More item variation in multiplayer - Where is my Gjermundbu helmet when playing Norse? Or my saxon chainmail? I would like to be able to select a wider range of weapons and clothing colours as found in the singleplayer, just to make me feel more immersed.
Well that's all I can think of for now, thank you for your work.