I always dread having to make a choice... Do I play the correct chord, at the correct time, or do I trigger the fill and Variation change, at the correct time..?

It's amazing how often they are the same time!

Watch many people's arranger demos, and you'll often hear most flubs (if they make any!) when trying to make that choice. Generally, turnarounds and section ends are when there are MORE chords than at any other time. Bad news is, this is exactly when you are also changing Variations, hitting fills, changing OTS and a bunch of other stuff too.

When doing most of that is as simple as tapping a button at your feet, why would anyone WANT to take their hands off the keyboard?

If you can work a sustain pedal (Donny has often posted he finds this tough, too!), you can work a few footswitches, and let your hands do what they are SUPPOSED to be doing...

Playing!