[Baal]

This would work well for Pirates/Nomads because you could limit the ship sizes and colinization techs.

It would work well to cancel off some of the techs that are included in Racial traits. Organic can only research Organic weapons.

You could link these anti-requirements into the culture you choose. Engineers are the only culture that can build Baseships. Worker are the only ones that can build Robotoid facilities. Scientists are the only ones who can build Central Computer Complexes. Xenophobes are the only ones that can build Citizen Data Bank facilities. The list is endless.

The possibilites are endless. This would really add to the game. Good Idea!