It would be nice if you could add an option (maybe in the config) in order to use cobblestone instead of dirt as a replaceable block for the builder when it works as a quarry.
I feel it's necessary when I mine in a mining dimension (like one of yours or the Aroma1997 one) and I don't want to leave big holes in the ground (and replacing with dirt isn't a good option, considering that the terrain is grass/dirt blocks everywhere). I hope I explained myself (english is not my native language).
Thanks in advance! :-)

Config option added for next release

Suggestion: Would consider providing an in-game UI for this option?

It would be great if it enabled the default block for the dimension(Overworld = Stone, Nether = nether rack, End = End Stone, etc.) to be the replacement.

@Sorbe That would be quite overpowered unless #1419 were also implemented.