I know that improvements are in the works for solving the problem with happiness of other races with Syntis controlled planets. 3 of mine are in correction mode now. One thing that would have helped was instead of seeing a -.50 happiness change would be to see the “real” value. My first take was build 20 force spawners. But then I did my own calculation and found I actually needed around 50 to get my happiness turned around. Simply fixing the calculation on the native race would be a big help while you work on better long term solutions.