I will repost here what I wrote in the change notes:

Finally added some long overdue additions that improve on the original idea.

The original changes in this mod to the base planets *have not been changed*. This update only changes how "Life-Seeded" and "Post-Apocalypse" faction ethics work (that start on a Gaia world or Tomb world respectively).

In keeping with the themes of a more "logical" habitability model, here is a brief explaination of the changes:

LIFE-SEEDED
In the vanilla version, Life-seeded species can ONLY exist on Gaia worlds... this really didn't make a ton of logical sense. Now granted, part of this is for gameplay balance, but to not be able to live on ANY other planet is really silly. With this mod, the more "temperate" non-Gaia planets will have a base habitability of 40% (Ocean, Tropical, Continental, Savannah, and Alpine) and the other four more extreme planets are set to 20%. This means that with enough tech research you can make other planets marginally habitable for your Life-Seeded species, but it will be very difficult for them to create additional colonies in the early game.

POST-APOCALYPTIC
In the vanilla version, you start on a Tomb world with various penalties to colonizing non-Tomb world planets. But again, this mod argues the point from a logical perspective that if a species can survive a harsh radioactive environment, they should be able to survive almost anywhere. This mod addresses this by making Tomb-world empires essentially "masters of none" in terms of colonizing planets. They start with lower base habitability on their home planet (60%), but they have this same base habitability on EVERY planet. This is similar, but also different than the species trait "Highly Adaptibe" which only adds a +40% buff to base habitation stats. This mod basically gives you a second option for creating a very adaptive species without needing to burn 4 points in your species traits.

I'm considering nerfing the changes to the LIfe-Seeded ethic a bit. Probably drop it from 40/20% to 30/10%, but I wanted more feedback before I changed it. Ultimately, I want the game to still feel balanced. The goal of this mod is just to create a more "reasonable" habitability model.