Hey, I was walking in adventurer mode, drinking at a well as usual... and then a !!mood!! struck me. I had to get into that well. One way or another. Shift-walk didn't work, alt-walk didn't work, u didn't work, and nothing I could think of would ever work. Which made me a depressed little cheesemaker until I had a nice dinner in a fine room. Obviously.
So, I'd like to suggest being able to hop into wells. And, since some are simply aquifer layers rather than other pools of water, I'd also suggest having some way to climb up natural and rough constructed walls (you could still build smooth walls out of blocks to keep people from climbing up them, or perhaps smooth existing constructions for the same thing. Alternatively, you could roughen up stone for dwarves that fell into wells and stuff... but then, why not just build stairs?). Even if there'd be no pathfinding support for that kind of climbing, it wouldn't break much if only adventurer mode characters could do it and doing so would slow them to 1/10th of their normal speed. Being shot at would pretty much interrupt all climbing and you'd fall back down so it wouldn't let you climb up something to escape combat and it wouldn't be that different from stepping off a cliff to escape either. It's very important, obviously, that the first step after you start climbing is still on the original spot, so your enemies can take full advantage of the 1/10th walking speed to get up to you and smack you around.