I wonder, would it better to just give a "battering ram" promo and/or treat it as an item that gives the bombard ability to a unit, or increases it by X amount if it already has some?
I am not sure if I understand correctly, but the problem is how to get any bombarding unit to the field. If we already have one there it is ok and no changes needed. And I do not think catapult or cannon would not benefit much from getting battering ram attached... It is only true for hill giants and treants and I do not see many of them doing siege.
It would be also harder to code - so my ram promotion just gives low (10%, no improvements possible) bombardment for melee units that do not have one. It would improve innate bombard abilities, but no melee unit have one.
Hmm...I never realized that Leader Promotion would change the graphics like that. If It would change back I might want to use that, but since it doesn't I probably won't. Does it stay when the unit upgrades too?
Well, as for the leader promo I did not realized that it would do what it did, too. I just wanted to see what if... I stoped using it, too. For two reasons - retaining graphics after split(i think even if unit is upgraded) and creating rams from combat xp. It was suprising to see "Battering Ram was born in Bannor city of Torrelial"
As for the battering rams, it might be a good idea to require some tech, but I am not sure. I just want some cheap early easily movable siege equipment. Now it is easier to capture big city with walls than early one with only culture bonus - you can use catapults or fireballs later and nothing at the start.
As for the other siege engines, I gave them all ranged attack - range 1 for catapults, cannons and trebuchets and range 2 for dwarven cannon (do not really fit the graphics...). AI uses this option quite well, but it was long ago I was far enough in the game to check.
I thought about making them capturable (I liked that much in Civ III and I think it is realistic). But I also want siege engines to be able to get promotions. So I left them some attack & defence, just lower than ranged attack. Currently I am thinking about giving them low speed free xp, but I do not know if it would not be overpowered.
As for the dwarfs carring the equipment, I do not think carring it over mountains is a big problem. It does not change much and you can always say: "only the trebuchet crew is going over, they manufacture a new one on the spot...". Harder with the cannons, but I still think it does not matter.
Carring more advanced siege machines by melee units is a good idea. I do not think it should only be limited for dwarves.
Most of the medieval siege engines were transported in inactive form and unpacked only for siege/big battle. It was especially true for trebuchets. The only thing I am not sure of is if AI would know how to use it.