[douglas]

This is possible, but it requires a little more work than that. Make each racial tech trait give a 1-level tech area. This is the only tech area that should depend directly on the racial trait. Then make another tech area that has that racial tech area (not the trait) as a prereq. Then make two versions of everything that tech area gives, one that requires the actual racial trait and another that requires the Assimilator trait.

With this setup, races with the racial trait can research their own stuff without depending on the Assimilator trait, but no one else can because no one else can get the prerequisite tech by any means whatsoever. Analyzing ships completely ignores prerequisite techs, however, so anyone can get that technology by analyzing ships that use it. Only races with either the actual racial tech trait or the Assimilator trait would actually gain any benefit from it, however, because all the components/facilities/whatever require the tech trait as well as the not-technically-racial tech area. With this approach, you could even make the Assimilator version inferior to the original to reflect that they're reproducing it without really understanding how and why it works.