As the cataclysm becomes steadily more realized on a z-axis, some things would be welcome additions:
Smashing DOWN or UP should be possible. Climbing onto a roof (Which doesn’t have bars) and bashing your way into the valuables is a viable tactic.
It is UNSAFE to stand on-top of a step ladder, but very possible. Being able to do so, with the risk of losing your balance if too encumbered / clumsy, or an enemy knocking it AND you over, would be great. Just having it exist one Z level up allows for better vertical traversal, as you could open a second story window, climb in, and pull your ladder in after you. Like a proper burglar.
Rappelling, via rope, would be an awesome way to scout out particularly tall buildings or deep chasms. And climbing gear for making ascents along a structure’s exterior would add a whole new dimension to scouting for loot. Just watch out that nothing FOLLOWS YOU UP, SWOOPS DOWN ON YOU, OR THE ZEDS DON’T START RAINING DOWN. Bonus points if spider mutants can just go up or down levels so long as a wall is adjacent.
Parkour Expert should probably allow you to pull yourself up onto 1-story structures with just one tile of wall. (Plenty of vids of that.) Either onto roofs or things that are 1 tile up that should count as handholds. (Rails, Windows, vegetation, etc.)
Street lamps and traffic lights are VERY climbable, and a great way to ditch enemies that can’t follow or knock it down, provided you’re near a window or roof.
Trees could stand to exist in Z levels. (Tree houses please)
These are just my stray thoughts on the subject for now. (Coding, I’m told, is much more difficult than just talking about things.) Hope at least one might be helpful.