As of now, in the Nightly version, the planets have multiple biome, which multiple subbiomes each. The problem being, more often than not the biomes do not go along all too well. To remediate to this problem, there could be biome groups (for instance, classed by temperature/weirdness/theme/difficulty) to allow a more logical biome placement. Ex: on a Lush planet, one could find a desert, a forest, a toundra, an ocean... but not a midnight biome or an alien biome. On a midnight planet however, one could find on one side a volcano biome and a frost biome on the other, separated by a midnight biome. I think this would be a great addition, esthetically and gameplay-wise (monsters from some biomes being way tougher).
Actually, I felt that was sort of already the case because I feel like we can generally already see some trends even with exceptions. What I mean to a degree is that it already feels like planets are already following a loose system of "biome groups", just with the possibility for the rare inclusion of biomes outside that group. For example I've generally seen alpine biomes generally spawn on lush or forest planets. Similarly, Eyes biomes seem to be strongly tied to alien planets.... but with the rare chance of spawning on others as well. It -could- be interesting though if those rare "nonstandard inclusion" of biomes from outside the usual groups also meant the possibility for monsters and encounters of a "nonstandard" difficulty for the planet they spawn on, however.
I've been wandering a bit, and it seems indeed that some biomes are more common on some planet types (finding tons of wastelands on volcano planets for instance), but there's the issue of having a midnight biome on a Lush planet, which do not fit at all (high ambiance and difficulty difference). And I think it would just make mord sense. About eye biomes, they are Alien minibiomes, meaning they are going to appear in alien biomes (whether on a Lush or an Alien planet). The nonstandard inclusion idea is a great one, but nonstandard planets would have to be somewhat rare.
