I certainly don't want ladders back.
The default ladders suit the job perfectly, as you can almost always break through. And if you can't break through the first, there's other ladders to use. As evident on the siege servers, its perfectly possible to break through somewhere.
Having only default ladders balances the game more, as it is easy to predict whats gonna happen.
Manual ladders makes it much, much harder to balance the game, as there are endless options with them. And it takes ages before maps gets rebalanced or removed.
I do agree, however that mauls are OP in sieges. But that can be said about many weapons that doesn't fit in sieges, they're mainly balanced for battles afaik. Take the pike for example, its pretty horrible in sieges, but a valid option on battle.
EDIT:
Forgot to add, it also makes more strategies viable!
With manual ladders, the only strategy used was "Camp the flag". Since you can't really know where the enemy is coming from, your best bet is to simply wait at the flag for the enemies to arrive. Which turns "Siege" into TDM with one team waiting and having a long respawn time, and the other team running and having no respawn time. Very little "Siegelike" to me.
With default ladders, more options become available. Since you can predict the enemy moves, you can prepare defenses at set places. eg: Ladders, stairs, doors and gateways. Making it much more "Siegelike" to me.