It's about usable Ladders
Sometimes you simply want to dig the floor under your feet, or at least the parcel in front of you, and climb down there. Okay ... some kind of Minecraft-feature, I know :P
But it would be great, as you could even make some kind of cellars, could bypass parts of the mine that you have set up faulty etc.
The ladder should be able to be nailed to a MINE-wall (only!), or you could have one that is 1-2 m high and could be positioned freely...
That goes in Hand with the ability to dig straight up or down ... not a ramp!