The Navigators +100% sensor range policy is very weak. It is used for just a few turns in the early game, and then its asteroid exploitation all the way. Later on there are just better policies to take.
However, one idea that could make it very attractive and fit "in theme" with the race. Keep the +100% sensor range, but also reduce Survey times by 1 turn. Now you have something cool and distinctive, giving these archeologists a leg up when it comes to surveying.