Most Happyness traits are not allowed by Hive Minded pops.
The Noxious trait is:
Roleplay wise it is a great idea. But mechanically it is seriously sub-par.
One idea would be -2% amenities consumption per non-Noxious pop if you are hive minded. This isn't nearly good enough (as -30% max habitability is much worse!) but it at least does something.
The Noxious trait is:
On a Hive Minded pop, this trait is horrible; the big benefit (+5% happiness and +2% happy per non-noxious pop) does nothing.
Roleplay wise it is a great idea. But mechanically it is seriously sub-par.
One idea would be -2% amenities consumption per non-Noxious pop if you are hive minded. This isn't nearly good enough (as -30% max habitability is much worse!) but it at least does something.