Try doing this scenario in UE4! You will give up long before you actually get to 128 brushes. I'm not saying this to bash UE4, but it's the fastest realtime CSG out there in the wild.
There's still a lot of work to be done, not the very least I need to implement a way to easily build and edit the brushes themselves. I also still have lots of ideas to improve performance even further and some ideas on how to bound floating point errors no matter how many times edges get split.