I don't feel any difference in the rate of agression from different minor factions... It seems kind of weird to move a peaceful explorer into a new System and suddenly get raided by "peaceful" Haroshem etc. 

I am totally fine if military/religious/economist factions do it though. 

Another thing is that they are all assimilated the same way. I think it would be great if for example:

• Economist ones could be bribed
• Religious ones gain more approval by spending influence
• Ecologist ones are cheaper for every population you have
• Militarist ones are cheaper for every ship you have
• Scientific ones are cheaper for every tech you have researched

I like this idea. It contributes to the "living galaxy" ambition. Perhaps also make assimilation costs go up or down depending on your own empire's political ideology so if your senate is controlled by ecologists, a minor faction of the same persuasion will find it more palatable to join your empire.

Good ideas. 

 I'm definitely hoping the devs have plans to flesh out the minor faction interactions, I don't remember seeing them in the GDDs.