@Zak, I gave your suggestion a go and while it certainly works, it's a rather cumbersome workaround. I definitely appreciate you offering a workaround and I thank you.
Here's how I envision such a play count/rating merge working:
In the duplicates manager dialog, if "delete" is selected in duplicates handling, offer two checkboxes: one for merge play counts and one for merge ratings.
If merge play counts is selected, simply sum the play counts of all the tracks to be deleted and the track to be kept. Update the track to be kept with the sum.
If merge ratings is selected, either average all ratings (only if rating != null, of course) and round to nearest half rating (or whole number if user turned off half ratings) or simply take the max rating and apply that to the kept track.