I enjoy 16 a great deal, as I believe do the great majority of others. It is the best par 3 on the Hackett, which does not have the best set of three's to be honest. The unnecessary blind tee shot on 2 is going to be fixed, 7 needs an entirely new alignment (it is an awful hole) and 14, albeit with a lovely tee location, is distinctly average. In that context, it would be nuts to mess with the most enjoyable short hole on the course. Standing on that high tee is one of the great locations in golf. Do you really want to abandon it?
Anyway, for the sport of it, let's assume your scheme gets the green light and 15 and 16 are combined. Where do we go for a replacement hole, ideally a par 3? Well, it has to be in the back nine of Hackett for starters and it has to be in combination with reducing one of the par 5's to a 4 to restore balance. What do you suggest?