I have been thinking about ways to make siege battles more interesting without changing the overall theme that these games have been going for. This includes the reintroduction of a mechanic from Atilla and applying it to the current wall template. That is the ability to mount artillery on the walls. But not only artillery, but also "weapon teams" as introduced in the recent DLCs.
My idea is for this to only be applicable starting at tier 2 walls in province capitals, so not all settlements will have them. Tier 2 walls you get one slot for artillery/weapons team and tier 3 you get 2 slots. These slots would essentially be a Bastion (google it for an better idea of what I mean), a section of the wall that would jut out a similar distance to how a tower currently sits out from the walls.
How they would work is pretty simple, if the settlement has one, during the deployment stage, the defender can assign either a garrisoning artillery piece or one in the defending army to "man" the bastion. Placing the artillery piece there for the duration of the battle. The crew can be engaged in melee and destroyed if not defended and the crew can also unman the equipment and get off the wall if it is necessary. Weapons teams which cannot man normal walls will be able to get on and off the wall only at this point and cannot move along the wall.
With the inclusion of this as a new feature to walls, I would also implement lightly differently as a racial buff to dwarves, who have really gotten the short end of the stick in regards to the settlements defences compared to their lore and to the original TW:Warhammer trailer which gave a very false impression of attacking a dwarven Karak. As a racial bonus I would do something similar to what the High Elves have, in that settlements with the "Elven Colony" trait offer more income and better garrisons to that of normal settlements. I would have provincial capitals also have a "Karak" trait on the campaign map. Which would include extra income and bolstered defences.
These defences would comprise of(in addition to towers) 2 Bastions and "Karak Gates" Karak gates would be a special type of reinforced gatehouse that would be larger and more imposing allow for weapon teams and artillery to mount and have a more reinforced gate. By doing this and allowing cannons and Organ guns to fire from the walls, makes the initial approach to the walls more daunting and punishing, which is exactly what assaulting a Karak should be.
This addition would make sieges more fun, and difficult when attacking. Currently, only mortars are really effective in defensive sieges due to their firing arc and I think there are a lot of really interesting artillery pieces that really struggle in these types of battles. Bolt Throwers, Cannons, Organ Guns, all of these types of artillery pieces have no place in defending sieges and are relegated to sitting far back from the walls to maybe shoot enemy units off the walls from the inside. This has always seemed like such a sad fate for these weapons. Weapon teams are similar. Their only use is on the flanks of the gate to shoot at whatever comes through the gate. Giving them a place, or even the option to deploy on bastions giving them 180 degrees of fire from the wall would make them very lethal if they are left unchecked.
Anyway, this is just a little idea I have had for a long time. I do think that if it is possible to implement, it should be. I think In Warhammer 3 with the Chaos Dwarves would be the perfect time to implement this kind of thing, and maybe give them some artillery and weapon teams that are specifically designed to take advantage of the mechanic would be great.