I'd like to propose that all blocks in the game are climbable with a specific delay to initiate and slow ascendancy. I.e. Walking up to a wall and pressing directly against it for 1-2 seconds will initiate a climb, the vertical movement is about 1/2th the speed of normal forward motion, and releasing the forward movement key automatically causes you to drop back to the ground.
The delay would prevent you from accidentally climbing everything you pressed up against.
The slow movement speed would prevent you from accidentally scaling and passing over one-block obstacles you didn't mean to.
The instant-drop-upon-release would let you quickly return to the ground if the other two fail-safes don't prevent you from mounting an obstacle you didn't intend to in the first place.
It'd be good fun to go climbing skyscrapers or scaling castle and city walls, and it shouldn't get in the way of a good "ramp" block or cause too much of a mess. Sans a handful of current titles, not enough games allow this today and I miss this feature from the few past games that did (Daggerfall, Arena, Thief 3, etc).
I like this but only for certain blocks, say a ladder block.
Well, I specifically suggested it so it wasn't specific blocks. I would assume that later versions of the game would allow for setting the properties on individual blocks (I would hope so), so it can be up to server admins and whatnot, but I thought it would be a largely agreeable default for the time being.
I think this would be good for certain blocks, and even then possibly not.
For example, have the cobblestone block and tree-wood block and similar blocks (blocks that would have natural handholds) be climbable slowly and with a delay, and have a ladder block that allows fast, instantaneous climbing.