Since you dont build settlements by yourself with sim settlements and due to this fact you dont get build XP, i thought about a Wisdom Injection Station (WIS), this is a new room with several machines that allow you to exchange Credits for Experience. The Base Ratio is 1:1, so you get for 100 spend Credits 100 XP.
But the XP is skaling with the levels of you settlements, while level 1 settlements provide 1% XP, level 2 and 3 will provide 3 and 5% XP of the base value. so having 20 level 1 settlements will net you 20 XP per 100 Credits. Having 30 level 3 Settlements will net you 150 XP per 100 Credits.
In overall this should be an optional addition like IDEK logistic station. I think this would be a good credits sink aswell.
But the XP is skaling with the levels of you settlements, while level 1 settlements provide 1% XP, level 2 and 3 will provide 3 and 5% XP of the base value. so having 20 level 1 settlements will net you 20 XP per 100 Credits. Having 30 level 3 Settlements will net you 150 XP per 100 Credits.
In overall this should be an optional addition like IDEK logistic station. I think this would be a good credits sink aswell.