Natural Design should get access to a modified Purity tradition tree.

[Dementor4]

Natural Design should be able to take a modified Purity tradition tree: it wouldn't let you mod your pops (since the whole point of the civic is that you don't do that) but it would instead triple the positive effects of your species traits, and halve their negative effects. Then their traits would count for double or triple (however the math works out to keep them on par, IDK) when it comes time to calculate their purity scores. So you can't get Fertile or Robust or Erudite, but instead your Intelligent, Adaptive, Venerable and Enduring species would become even more intelligent, adaptive, venerable and enduring.

 

[Nabil ad Dajjal]

IMO the real problem is 100% with the flavor.

From a mechanical POV Natural Design is doing exactly what it's supposed to: nice boost upfront but long term worse than picking an ascension path if you don't take advantage of the snowball. The issue is that it reads as identical to Purity, even with the unique building being damn-near identically named to the biomorphis building.

Change the name from Genomic Services Center to anything else, with culture workers instead of medical workers, and it's fine.

 

[Red Death]

3 of the 5 Purity traditions are directly tied to genetic modification. Some of the Authorities have the same problem, and some at least do in their description. So immediately, most of the tree needs to be replaced for this. Also, how would the Biomorphosis situation work with this civic?

The only thing that makes it look like Biomorphosis Purity fits with Natural Design is the name "Purity" (If you look at the contents, you could say it was just misnamed). It's mechanics and even flavour/description run counter to Natural Design.

The design intent with Natural Design is also explicitly to not take any Ascension with them.

it would instead triple the positive effects of your species traits, and halve their negative effects. Then their traits would count for double or triple (however the math works out to keep them on par, IDK) when it comes time to calculate their purity scores.

I do like this idea! But perhaps it would be better to do it in a different way that does not need to be shoe-horned into an Ascension Path that does not really fit?

It could be part of an Ascension Perk, a tech available to empires with this civic, or even just included into this civic by default?