No stone mode
I suggest a new mode where you could not make quarries, tunnels or landscape.
So you could have stone only from the boulders and would be forced to use your stone and minerals wisely and make wooden fortification.
I think this is actually already possible in any mode.
In the presets, there is a command, I don't know it's actual function but it reads:
You could attempt to change that to false.
edited July 2017
I've tested it: it does not do that. Perhaps it prevents the corruptrons to dig the ground.
That may be true. Someone from Sauropod may let us know if this possible, and what that flag does.