Harder minor faction assimilation

Agree with everything above.

The 'Assist' quests are also far too easy, and there should be relationship point threshold to be able to start them.

I don't know about 10 turns just to assimilate them, but .... even if I've been blockading their system for 100+ turns, and their relations are at the worst possible .... I can usually burn enough influence to immediately make them my BFFs and then assimilate them all in a single turn.

A good way to slow that all down, I think, would be to limit you to ONE of those actions per turn.

It all depends on your current relationship with them so it doesn't have to always be 10 turns.

Main change that should be easy to implement would be to limit the improvement of relationship to once per turn.

Once that is in place and we see how it is working out we can work on the details.

It should be a dilemma to assimilate or not to assimilate, with clear bonuses and drawbacks for each. Form a federation/alliance with minor factions vs. assimilation. For ex. - if a science based faction forms a federation with industrialist minor it receives an industrial boost. The same faction would be less interested in federating a science based minor, because its own affinity is greater than a boost received from a science minor. If either is assimilated - there will be a new system and pops belonging to major, but no faction boost. A minor could also provide resources to a friendly/federated major, maybe even military units. Maybe it could provide a design for unique buildings/improvements or ship modules? 

If there's a galactic assembly feature, allied minors could provide votes for your cause. 

They should really have all the same diplomatic options as majors.

Assimilation should definitely take longer/more effort or resources.

Right now the minor factions are very shallow and empty parts of the game.