It would be nice to have a library of CSGs available, rather than the tedious copy and pasting. A new tab on the existing UI could house all CSGs, making it super easy to drag and drop them onto a planet. This, mixed with bug fixes and real additive and subtractive brushes (like Spore and Modnation racers) would make the perfect system editor.
There is a code piece in the editor for this since a while. Some dev at Uber had this in mind. I guess (and hope) it's just late.
Like, a drag-able and sizeable circle BRUSH, that affects the planet in real time, rather than the awkward crater brushes with an already defined shape.