I would not mind them being reintroduced, but as I said already, they would change the balance in siege a lot. It also allows for many more griefing opportunities. (the hatred when you place a perfect ladder only to have it destroyed by an asshole teammate seconds afterwards...)
Anti ladder ladders would also become problematic, like in strategus.
With active admins, and people willing to revisit maps and make adjustments, it could work. But I am not sure that it is worth the effort.