Now that the game’s out and been out for a while, I would like to ask if modding terrain generation is possible, and to what extent?
[Paging @RepeatPan, @honestabelink]
I haven’t looked into terrain generation too much. @RepeatPan has done work great with it in the past so I would say wait for his response too, I will also ;). I recently jumped into it a little bit for my “startup script”.
Terrain generation is still only modable through overriding the .lua files that control it. So any approach to it will lead to compatibility problems between other mods doing the same type of thing. We would need a base to work from again… @RepeatPan.
Another side note is that world/terrain generation is still a work in progress. I personally wouldn’t want to sink much time into something that is likely to get an overhaul ;).
Overall, Is it doable? Without a doubt.
Could you have sliders to control world gen? Absolutely, though I wouldn’t be able to say how much work it would be without truely sitting down and looking over everything.
It is a great idea though. 
One side of world gen which is really approachable now is spawning entities around the world, such as new flowers, animals, ect. This side is achieved with just a mixin and a few files.
Again great idea’s everyone.
For what I’ve seen of it, terrain generation consists of 90% evil voodoo magic (i.e. maths) and 10% “I have no idea what’s going on”. But the break down is this: It should be possible to mod the terrain generation to create at least hilly terrains (so cliffs and “sky islands” like in Minecraft may not be possible).
I honestly have no clue where I would even start with modding. There’s blueprints, there’s meta data for those blueprints, lots of filter functions and at some point, these 2D arrays get magically turned into terrain - likely on the C++ side.
So: No, not really. It’s not feasible at this point to even start looking at it.