I have experimented using macros to create inverse traits before with mixed results (as in, i made every combination - skipped adding unique icons or text and used their filenames to test) - and it was .... really underwhelming. Just echoing what others have said in that you end up with a ton of pointless downsides.
Traits need to be specific in their bonuses to promote strategy, but not too specific as we cant govern pops too tightly (for ui and micro reasons) - whilst negatives should always have "some" impact, but under certain conditions (such as when their positives are active too - if a mixed trait) they can be more pronounced). I think what makes a good trait for me is putting them in to categories like these 4:
- leader effects (i.e. leaders made from that species)
- custom leader traits, leaders spawning at higher XP levels, leaders not costing unity
- e.g. a hive-only "larval gestation" species trait could have leaders cost 25% unity 75% food[minerals if lithoid], so you can spam out leaders without hitting your unity budget.
- A machine version could have them cost energy and level up faster but be more accident prone (Overcharged robotics or something)
- And a corporate version could have leaders cost consumer goods, for example (youre literally bribing them with a mountain of wealth to come work for you).
- resource effects
- Positives and negatives tied to output of resources generally (not by specific jobs). so rather than being a "skilled clerk" trait [bonus when working as a clerk], you are "trade savvy" [just bonus output full stop] and that pop puts out more TV in any trade value yielding job - such as a merchant (this might be a bad example specifically due to how TV modifiers work, but it illustrates the point).
- strata effects
- Positives and negatives if working in X strata [particularly strong for gestalts with only 2 strata and no demotion time lol]
- Might be a good way to influence political power.
- "Born To Serve" - an engineered trait, makes these pops particularly happy in the servant and slave strata, but if outside of this, they struggle with individual agency, prone to outbursts, leading to reduced happiness and increased political power - but they cant shake off their genecoded work ethic - and keep receiving slave bonuses (or a mirror of them, for technical reasons) even as free pops. So they work hard but are a pain to work with if given freedom.
- planet effects
- Positives and negatives from planetary stats - crime, carry capacity, housing, amenities use and so on, or with certain planetary properties. Like:
- Orbital Denizen - this pop is happier (and has reduced amenities usage) when on a planet with an operational orbital ring).
- There is also the potential to do swaps like, "Singing flora" this plantoid pop consumes more food (or energy if photosynthetic), but in return they consume no amenites, and actually produce 1.
You'll notice the absence of job-specific traits - "natural born priest" or whatever - I don't really think they work well with how the game is set up, you either end up hyper focussing pops and planets to use certain jobs, which encourages micro, or it feels like a wasted/false choice.
If a trait plays in just one category it gets +/-1 point. if it touches 2 or more it could get +/-2 points, adding or removing another point if mixing positives and negatives, and one more +/- based on the overall magnitude of modifiers involved, as a rough if imperfect balance regime.