A quick update to the original mod for those who, like me, want to quickly get rid of annoying cliffs on their interplanetary factory. Original mod -> Mineable-Cliffs

Allows players to slowly mine cliffs prior to researching cliff explosives. This defaults to requiring Steel Axe and taking 15 seconds. The Steel Axe requirement, the mining time, and whether cliffs drop stone when mined are all configurable. Bots still require explosives to remove cliffs, so automating removal still requires research.

The intent is to fix the binary "impossible" vs. "trivial" nature of cliffs and cliff explosives. Cliffs in vanilla can be frustrating because certain orientations cannot be crossed by yellow undergrounds, and long lengths of cliff can significantly increase travel times. Once you get access to cliff explosives though, they're trivial to deal with. The problem is that there is no middle ground. If a cliff is causing a major headache, you can't knock it down until you research the explosives. The reward of getting the technology is soured by the pain to get there.

This mod gives you the option to get rid of a cliff that is seriously in the way of something important, but the time it takes to remove cliffs means that it is not worthwhile to remove them all by hand. That means that cliff explosives are still rewarding to get to, especially since automation still requires them, but the frustration of dealing with cliffs early in the game is alleviated.