I don't know wheter this thread was discussed or not, but I didn't find anything special. I think that some kind of logic should be added to galaxy-generator, and particularly to distribution of anomalies/wonders. As for me, some list with allowed types of planets for each anomaly/wonder should be created. For example:

Tree of Worlds can only exist on Ocean,Terran,Jungle,Arid,Tundra planets.

Polaris Workshop - Ocean,Terran,Jungle,Arid,Tundra,Desert,Arctic,Barren,Lava(everything is possible, but it can't exist on Gas giant, really).

Corrosive Soil - can't happen on Gas Giants and asteroids.

Komatiite Voolcano - can't exist on Gas Giant and asteroids.

Also, some effects are more likely to drop on some types of planets, for example:

Strong Magnetic Field/Rings happens more often on Gas Giants



Also, I've noticed that something like that already exists, for example Garden of Eden can only exist on Ocean,Terran,Jungle,Arid,Tundra.



And some examples: