This addon looks great and would be a great 4 space replacement for after Matt finishes the recent version and abandons it... only thing stopping me from switching to this one is the ore distribution not being like galacticraft and the terrain gen for planets. I personally don't like the 1 block from top to bottom when it comes to underground, just doesn't fit the minecraft feel.
Then theres the testing I did in creative and how ores seem to only spawn on the diamond layer of planets instead of all over like vanilla and galacticraft. Didn't fit in my book, maybe add some planet based blocks to spice up terrain like certain planets have gravel, sand, dirt or whatever would fit on certain ones?
Just my opinions on what should be tweaked really, don't mind my rambling though