Think bigger!
How about moving bases?
You grab the flag from the enemies base, after you find it. Then have to locate your base has which has also moved.
Literally one of the first things I thought of.
Not just doors, but traps in floors, that open as you run across, maybe color coded to other objects (light colors?) so you can see a pattern, get a little F(irst) P(uzzle) S(shooter) action going. Maybe it drops you to your death or just how you access another floor, or pops up mancannons. Multiple actions to fire off a script was mentioned. Depending on capabilities making it where members of your team have to shoot or stand in a certain area to unlock access to a Rocket Launcher or Scorpion for example.
I've always wanted to create a map that changed flow as the match progressed. Kind of like invasion, but not so much built around attack and defend. Start of where the teams are separated and first have to get through a barrier to really engage, but have the ability to take potshots at each other, then break out of a building into a larger space (think lockout to avalanche) and have weapons spawn in different areas as the action moves through the map. Obviously going for a different kind of action than a typical Halo MP match, but I like that is sounds like the new tool-set may be able to let me finally do it.