My term for centerline bunkers is "a dual fw hole." While the 4 options are true enough, they come with caveats IMHO.
The layup option is the only predictable one.
Carrying it? Depending on tee and hazard placement, the carry option is only realistically available to a small subset of players. When I did that, I made it a challenge for the back tee players, maybe a 280-290 yard carry, while arranging middle tees where the carry is typically substantially easier, to make it fun, i.e., from tees where I expected players with 225 drives and 200+ carry, place the hazards at 190 max from the back of their tees, so the max test of carry distance can be achieved, but where it easier on most days.
Left and right options? Unless there are fairways on both sides with statistically adequate width, i.e, 30 yards, that won't really be an option, i.e., two separate fairways. I do agree that any shortest route should have a slightly narrower landing zone, like 25-27 yards, so taking it requires the best accuracy you have, while the longer route should be substantially wider, even with a longer approach shot.
I also agree with no more than 2 per course - I don't see it as such a great idea that you would need it more than twice in favor os other tee shot hazard placements. As suggested, the tee shot on a shorter par 4 to create interest, and the second shot on a par 5, where the alternate fairways may provide an angle advantage, driving the hazard is required to reach the green in 2, and/or laying up increases approach shot distance considerably. If the approach is still under 150 from behind the bunker, it probably doesn't matter much, but going from 100 something to over 150 might make a difference. That suggests CL bunkers in those areas may need to be a bit longer to accommodate the various positions of different tee shot results.
Tommy's example of the green running away from you might make as much sense as avoiding frontal hazards, depending on the approach shot length. However, from that picture, I wouldn't anticipate too many people going left....the right is just too inviting and shorter. I may be wrong judging on a picture, of course, but I am suggesting that the details of placement, if not done close to perfectly, may make the centerline just annoying and reduce its design effectiveness.