Minors shouldn't be affected by cultural defection in home sector

Minor races in Galciv are minor in all but name and I like it that way it makes the game more interesting. Minor races often have lucrative planets, have little problem keeping up with tech, frequently have large fleets and can often call on friends in wars due to their lucrative trading routes. Beacause minor races can't build defensive starbases against the culture of other races their world can easily be made to defect with few problems. And the race that a minor world defects to gains an awesome world without having to conquer or colonise it themselves and without having to build any of the improvements. Beacause minor races never colonise outside their home sector worlds in this home sector should be immune to culture but only worlds in their home sector. Either that or they should be able to build "defensive" starbases.