Just to clarify a few things:
1. The ride computer (PLC) will only take into consideration what data the programmer is giving it. For instance, it will not take the weight of the train into effect unless there is a scale and it is programmed to weigh the train before each launch. From my very good knowledge of Verbolten, I know that the train is not weighed and really the only data the PLC is using to launch the train is how fast the train is moving at any given time, though the use of track sensors and timing how long it takes for the train to go between them. The PLC will then adjust the launch speed to reach a preset speed by the end of the launch, using an algorithm known as a PID loop. If a train is going slower, it will adjust the output of the motors higher to get it to reach the desired speed. If it is going faster, it will slow the motors down as to not launch too fast. All of these calculations are happening very fast and are recalculated every 10-50 milliseconds, depending on what the programmer has setup.
2. I do not know if maintenance is able to adjust the speed of the launches, but I would assume not, given the disastrous consequences if they got it wrong. Chances are that the final speed is hard coded into the program and it would take someone to open up the program and make the coding change to change it.
3. To answer Mike's original question, sure it could. PLC's are very versatile and pretty much you can do anything with them given the right input. If you gave it weather and other data, you may be able to program it to auto-adjust the final speed to help it throughout the course. However, if a ride's functionality changes based on the day, ie it will make it around at some times, but not others, it has some mechanical design flaws that need to be accounted for. To my knowledge, the only rides that have that bad of a problem are KK and TTD and well, you see why no one has built others like them. Even they will usually only have issues on cold windy mornings, but will make it around any other time of day.