A few tools we need. Perhaps magic or perhaps technology. Ideally ambiguous but that's hard.
A pick or stone digging tool that breaks the block you're aiming at and the block below it but will not break anything 10 degrees below the horizontal eye line. The eye line is the camera to cross hairs. This would produce tunnels with level floors with no accidental holes faster.
Wet concrete. A concrete made from concrete and 2 stone or water and 3 stone. When placed as a blob it fills the targeted location and the two either side, right angles to the player facing. This fills the gaps that sometimes form because there is no contact surface that can be targeted with a blob. This becomes a floor of stone not blocks.
Guide line. placed on the floor like a touch mount. Spawns an intangible beam/ string 32 blocks long in the direction it's facing. Again straight tunnels.
Crowbar. 1 small iron rod, one large rod. Picks up workbenches etc but only if they have been placed in the past 1/2 hour. If workbenches etc are older then it only works in protected areas with the user being the owner. Lua scripts should be able to do that.
Fallen columns. A tool or recipe that rotates cylindrical blocks 90 degrees so they can be placed that way creating everything from fallen pillars, logs, log cabins and pipe works. Ideally it creates a new stack for ease of use. It should also rotate half cylinders since those should make good roofing tiles.
Can we use blocks from the blockbench as ingredients in recipes?