Basic Imperium of Man:
Spiritualist, Xenophobe, Militarist
Theocratic Oligarchy
Communal, Conformist
Decadent, Weak
+50% Alien slavery tolerance
+50% Alliance cost
-10% Army damage
-30% Ethics divergence
+10% Happiness
-10% Resource output without slaves
+25% Rivalry influence gain
+5% War happiness
+50% War tolerance
+10% Xenophobia
Seems legit. Could substitute Rapid Breeders for Communal.
I was thinking about it but I don't think the Imperium of Man is communal or conformist, though it's certainly decadent and weak. (They can't even function as a society without servitors)
On the surface it might seem communal and conformist but if you know anything about the Imperium is that it's only loosely tied together by worship of the Emperor. Across its countless worlds and countless hegemonies are countless ruling styles which can be somewhat loosely classified into things like Feudal World, Hive World, etc. They mostly do their own thing except they pay tithes to the Emperor and worship the Emperor in some way and even the manner in they worship can vary quite a bit between worlds. Many of them associate His worship with the worship of their local sun for example.
Many worlds which have fallen technologically and regressed socially now have planetary governors assigned by the Imperium ruling over them in a space station while they live out their lives in a sort of medieval / primitive state. Worlds are so completely out of touch with each other that it's common that planets which have been completely eradicated of life for years can go unnoticed for decades or centuries.
So really, it's about as communal as we are communal today, which is to say not very communal at all. They're definitely rapid breeders though, as they're the only ones other than the Orks who's main strategy is to throw bodies at things until they die.