My suggestion is to allow all Ethos access to Slavery by adding an extra Species Rights and a building call Prison.
New Species Rights (Any Ethos can select and is considered Slavery for all game mechanics):
New Building:
Prison: Building gives large amounts of Energy, Minerals, and Social Science. Pop must be part of the False Citizenship Species Rights group to be place on a Prison building.
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http://www.historyisaweapon.com/defcon1/gilmoreprisonslavery.html
https://en.wikipedia.org/wiki/Penal_labor_in_the_United_States
Above is a links to an interesting articles about the connections between Slavery and Prison. I would argue that any government with any Ethos can use penal labor as a type of slavery for profit.
New Species Rights (Any Ethos can select and is considered Slavery for all game mechanics):
- False Citizenship: This represents targeted imprisonment due to specific laws created in your society that target this species. False Citizenship pops have all rights of a Full Citizenship Pop but can also be placed on a Prison Building. Pops in prisons create large amounts of unrest on planets to represent the "Crime" increase that is created by these laws.
New Building:
Prison: Building gives large amounts of Energy, Minerals, and Social Science. Pop must be part of the False Citizenship Species Rights group to be place on a Prison building.
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http://www.historyisaweapon.com/defcon1/gilmoreprisonslavery.html
https://en.wikipedia.org/wiki/Penal_labor_in_the_United_States
Above is a links to an interesting articles about the connections between Slavery and Prison. I would argue that any government with any Ethos can use penal labor as a type of slavery for profit.