For my part and based on the use I give, I only miss two things:
Full automation. For the cases in which I need it I have to do the mastering in Cubase, and it does not work in the same way.
More slots in the master section. The current limit of 12 inserts seems to me an important limitation, and unnecessary in the current times. I currently have to master using the VST Blue Cat’s PatchWork. By my way of working I have in my mastering template 25 VST, very far from the 12 allowed. It would be good to break those limitations.
Otherwise perfect, I love WaveLab!