Laser sighting might be good as an aid to the driver, but I don't thing a path guidance system is even close to being required, especially with the new boats. There have been and continue to be a lot of great drivers out there that can drive a straight line so if they know they are on center they can keep it there. Even with the new boats (and certainly with the old boats) if you react to what happing you won't drive straight, but if you are pro-active and almost anticipate what to do, the boat path will be nearly perfect and certainly better than any mechanical/automated system. Rails systems will kill an already dying sport, I don't know about you, but the skier to boat communication/interaction in both practice and tournaments is a big part of the sport for me, which last time I checked, is suppose to be fun.
I do think there are some positive merits to speed control and a focus on improving those systems is where the effort should be made. There are too many good skiers that are being penalized because their style or size adversely effects the boat pull quality. Again, systems that react will never match a good manual driver. I use to drive each skier at near perfect actual times (even with all buoy timing) and many skiers assumed I was driving on the slow end of the tolerance. That being said, I do like the concept of speed control and my arsenal of drivers has expanded dramatically. However, when the best pull you can receive is achieved by not actually engaging the system, there is a problem.
Perhaps the speed control systems could be programed to allow a bit more deviation from buoy to buoy, that way if I skier digs in deep on one term they won't be blasted into the next buoy just so the time can be perfect for the next timing segment. How about a rope load sensor, like Jump, to help the system determine when and how much throttle is required. Between that and knowing the boat position in the course, a more program could be developed that could be fair to all skiers. Perhaps this has been attempted without success, I know Perfect Pass used a load sensor for slalom.