Transparency and Z depth control need numbers beside sliders to show precise values the designer is entering.
There need to be precision methods of finding out the exact X,Y,Width and Height of things like Activation Regions, Filled and Wireframe Regions, current actor position, more floating numeric info in tooltips on workspace.
There need to be tools to align, center, size and orient actors as groups on the workspace, so you can make sure the left sides of buttons are all lined up or centered on a specific line, etc. ... what would really help is arbitrary magnetic lines on the workspace like in .NET that show you where your actor is lining up in relation to other controls, etc.
Snap to grid needs more info and control for activation regions.