Lowering the bonus would also harm many players who are in dead zones, so I don't think that is a solution, just a new problem. If you happen to have one or two neighbors who DO play with you at the right times and they are the only ones who visit you, then dropping the bonus while those few are there would do equal harm. So, no, I don't think that would be of value. In fact, lowering the bonus would only be a detriment to many.
I know ddevil wanted me to move the idea, but I will reiterate it here, that perhaps allowing us to choose an extra 4 hour culture bonus if we go visit all our neighbors would help solve this. It would encourage people to visit their neighbors....it would give you an extra 4 hour time window if you are on a different playing time zone than your neighbor....and it would offset the fact that some players get help by doing absolutely nothing all the time. (The rest of my idea was that if you visit all your neighbors you could choose to either get a 4 hour culture bonus, an extra 5% builder time, or an extra number of coins....your choice each 24 hour period....that way you get rewarded for helping your competitors, it encourages neighbor visits, it helps those in a dead zone, and rewards those later in the game when going around to a gigantic neighborhood is a pain and encourages them to visit all players, not just the ones they know visit them back, and it isn't so large an additional bonus that it would throw the game off kilter.)
Forgive me ddevil, I don't mean to step on your idea, but if the only way this gets forwarded is if it gets tweaked, at least this tweak wouldn't cost us.