I play principally mutliplayer and here's my thoughts.... As another poster mentioned, what is needed is more gameplay elements, the bits that repeat many times. If you make (for example) swinging a weapon more satisfying that improves everyone's game many times.
1: Tighter multiplayer map design. I've seen some new Siege maps done by the fanbase, they aren't bad but I haven't seen any classics. TW could also release a few better designed maps.
2: Custom designs for armours, weapons, shields etc.
3: More excitement in battle. More blood splashes, more painful screams, battle cries initiated by players, simple emotes such as gesturing\saluting with weapons or cheering, simple standard bearer, commanders, musicians - anything to encourage clan play organisation in battle.
TheDuke