Having the slavery system from AGoT is a great idea but it has some problems and there are a couple things to adapt it to the current setting.
My suggestions:
1. Make slaves obtainable by raiding. not just character slaves but camp slaves. Every time you conquer a town holding there should be low(around 10%) chance that you get an upgrade to your slave camp level. It shouldn't happen often but raiding a whole realm with your horde should bring a sizeable quantity of slaves to your capital
2. Make slave trade more common. In AGoT there is a continent that doesn't practice slavery and another one filled with republics. Lux Invicta is different. Therefore i suggest that the possibility to enter slave trade be available to every non tribal realm(charlemagne) with access to sea. If you could limit it to realms with capital next to the sea it would be great. Maybe impose a stewardship limit but that would take effect only in the case of a feudal realm.
3. Reduce the price of slave camp level. 400 is a lot and the AI barely gets that rich. It should be reduced to 250 or something like that,
4. Make an event allowing to a slave owner liege to give slave camp levels to his vassals(the condition would be having a max level slave camp in your capital). this way slaves could be divided across the realm in the lands of the slaver vassals while not in the lands of those vassals who do not practice it. It would improve relation and the liege might be paid less that in a normal transaction (maybe 100).
My suggestions:
1. Make slaves obtainable by raiding. not just character slaves but camp slaves. Every time you conquer a town holding there should be low(around 10%) chance that you get an upgrade to your slave camp level. It shouldn't happen often but raiding a whole realm with your horde should bring a sizeable quantity of slaves to your capital
2. Make slave trade more common. In AGoT there is a continent that doesn't practice slavery and another one filled with republics. Lux Invicta is different. Therefore i suggest that the possibility to enter slave trade be available to every non tribal realm(charlemagne) with access to sea. If you could limit it to realms with capital next to the sea it would be great. Maybe impose a stewardship limit but that would take effect only in the case of a feudal realm.
3. Reduce the price of slave camp level. 400 is a lot and the AI barely gets that rich. It should be reduced to 250 or something like that,
4. Make an event allowing to a slave owner liege to give slave camp levels to his vassals(the condition would be having a max level slave camp in your capital). this way slaves could be divided across the realm in the lands of the slaver vassals while not in the lands of those vassals who do not practice it. It would improve relation and the liege might be paid less that in a normal transaction (maybe 100).