I am personally happy that SetToolbar is not supported :-)
Having classic PB toolbars that can be aligned vertically (or float) in a Web application would really be unpleasant IMHO.
I prefer to define a unique toolbar in the MDI window, and have some of its buttons (typically the rightmost ones) that show/hide "as needed", depending on the current visible sheet window.
You can do that implementing the activate/deactivate events.
My 2 cents.