I'm still not sold that the idea of getting techs from conquest is a good idea in any way to begin with. I don't think that if one nation were to conquer another that they would be able to understand everything that the people they conquered understood. If what you are proposing (and what was in Civ II) were always the case there would have been no Dark Ages.
Maybe, just maybe there should be some sort of tech advantage or gifting through culture flipping, just because that's technically your people who live in the city with that tech.
