Ironically, I'd probably be better off if we don't swap because someday I want to kill that dang old witch and the easiest way to do it would be stacking 8 siege engines. The change might be better overall (hard to tell really the long term ramifications of it since we've not really gotten into the late game pvp where siege engines would see the most use I think) but I'm gunna have difficulty looking past my own selfish short term self interest

If this rule is going to be changed, we should be careful to reconsider the cost and durability of siege engines. These currently last only one combat round. As it stands they are expensive and good. Let's not make them expensive and bad.
I totally agree that we should be careful of changes, but also I sorta think that as we move out of the early game and into the more mid game the economy of the game is changing a lot. In the first few turns they were expensive as there were some forts that needed to be sieged and most people were on 0-1 wood income, but I'm not really sure if they really are expensive anymore? I'm making 3 wood a turn, Wright is making 3 a turn, FitzHarbort is making 4, Ayes is making 5! considering that it's not every turn that we are besieging down a place (at least for the moment) woods really stacking up quite quickly. And we've not even conquered half the map yet. Similarly armies are now sorta lowish value, whereas in the first turns everyone was buying them for 2 gold each, but as everyone hits their army cap and gathers more villages we are reaching a point where loosing armies doesn't really matter that much, and army cap becomes a much more valuable stat. So long as our actions are limited by our army cap our resource incomes will keep going up but our ability to spend that income won't really go up with it, which I think will make things like siege gear better but also cheaper.
Right now I think the only really valuable material is stone, since it can raise army cap, and gold, since it can buy stone.
If this rule is going to be changed, we should be careful to reconsider the cost and durability of siege engines. These currently last only one combat round. As it stands they are expensive and good. Let's not make them expensive and bad.
It's a good point. Destroying walls on long seiges is useful (essential vs. anywhere with a Keep), but killing defenders is strictly better. Maybe they don't get exhausted?
I think that if they don't get used up that'll mean pretty much everyone just buys 5 (or however many to make 1 kill a wall) and then never buy any more ever again? I'm not sure if that's what we should aim for, but then again maybe then people might eventually buy bows.