I had a couple of ideas but some would be too hard to explain right now.
One of my better ones was a siege map that would be a three-story bank. With a firescape, roof opening, and windows.
Basically two teams one in the second level of the bank. The other on the outside (not a big area outside) just a surrounding area. Then the outside team could choose to either go up the ladders and enter through the roof or windows. Or you can enter through the front door. Then the team on the second story has to protect the flag from be captured from the vault. Then it just becomes who can steal or protect the flag from the 2nd story vault. If you like the idea I can give you pictures for ideas.
Edit: Then it can be more like a staircase But is it a good idea?