Is it possible to remove the ground alltogether so I can build inside it?
As in load a save and attach bricks to it.
Yes!
If you download the newest version of the Space Pack as well as the map properties loader support script, it includes a /toggleground command that will allow you to remove the ground.
Unfortunately, RTB messed up and it didn't push the update as a new notification, and I want to actually make some changes or something before I justify updating the file and making ephi approve it again so that it sends that push notification and updates the version.