Subjects:

Q: Are subjects forced to join some federation types (or all?) if you ask them to?
A: It’s up to your federation whether or not subjects are allowed in. If they are permitted, they will automatically follow their overlord in or out.

Q: Can you make/start a federation with your subjects?
A: Federations are (theoretically) alliances between equals, so independent diplomacy is required to initially form one. As noted elsewhere, vassals may be brought into federations (whether they like it or not) depending on federation law.

Q: Can you form a trade-league with a 1-planet sector you released as a vassal for just that purpose?
A: No and yes. Yes, you can release a 1-planet sector with the intention of starting a federation, but they would need to be independent for you to be able form it.

Federation Laws:

Q: Will there be any tools (laws, for instance) to combat ethics drift within a Federation? It would be nice to have a way to deal with an incompatible empire other than expelling them (then reabsorbing via a liberation war).
A: No, there is no way for you to influence the ethics of other empires. The cohesion penalty is meant to be offset by having to assign more envoys to the federation.

Q: Can you pass federation laws regulating member policies? For instance, decree that all primary species must have full citizenship throughout all federation empires? Or just outlaw slavery altogether? Because I hate seeing my own species enslaved by allies I have a migration treaty with.
A: There are currently no laws to influence other empires like that within the federation, but we’re certainly open to the idea. Once Federations is released we’ll be gathering your feedback as always

Q: Will we be able to pass laws that affect specific pop types? For example, I want to have all empires in my Hegemony, or all my vassal empires be forced to set Starfish pops to purge status (after all everyone seems to think that Starfish portrait represents fanatic purifiers the best).
A: Same as the answer above.

Q: How many federation laws are there?
A: There are currently 14 categories of laws, with each category having 2-5 laws.

Q: Can we get an Academic Debate succession type for Research Cooperatives?
A: There is in fact a Challenge Type called Thesis, which very much mimics what we think you are looking for. It’s available to all federation types.

Q: Could we get an example of more federation laws?
A: Yes we can! In dev diary #158 you could see most of the laws, but there are some things that have been changed or added since then. We now have the Strongest Succession Type, which is split up into different categories like Economy, Fleet, Tech or Diplomatic Weight. We have also added two new Challenge Types: one which is a bidding process where you spend ECs to become the president, and another one which is an academic thesis. We will definitely show off all these things in more detail on a stream sometime in the future.