I can confirm:
- Marauders have not taken slaves for a long time since the update which made them freindly towards AI empires
- This change has been lifted yesterday and Marauders are conducting attacks against neighbouring empires
- Slave pops of neighbouring empires has also popped up again but this seems hard-coded and not a result of raiding
Note: Even though Marauders had a masive raiding fleet available to them and have beaten the defending fleet and invaded the planet, they did not raid. During the attack they actually sent all of their transports back to their base (for no apperant reason as they have initiated the attack to no retreat was necessary from the enemy system) and have only invaded with groundtroops carried on their Command Cruisers
I agree that in the early game the player would mostly not notice the Raider activity against AI colonies but from mid-game on they are visible due to alliances and shared vision thereof, and since lost colonies are visible via the territory border system. I would advise against automated slave pop generation from neighbours as it is appreant from mid-game on and it seems that a dynamic slave economy is attainable and would be in line with the games credo of every event taking place on the map: I have seen Marauders raiding my colonies numerous times before and thus the only major obsticle should be if the AI can take the occasional beating
Solution might be dynamic relationship:
Every 10 Turns,
If AI is stronger then Marauders attack 60% of the time else accept paymanet
If weaker and payment<80% of income then pay 75% of the time else hostile relationship
This way, financially rich empires mostly avoid being attacked but would sometimes be attacked and strong empires would eventually attack Marauders
Will start a new game and check if the AI can now handle the Marauders and still remain competitive
Update: The Marauders are doing much better now then the last time I saw them attacking as they are now also capturing ships (for which their Command Cruisers are in an optimal position) - they for sure do not need any buffs: hopefully the AI empires can keep up