I have written a simple script that renames the .desktop file (if it exists) inside the .tcz of an extension, and this satisfies my requirement of a given app not showing up in wbar, and neither does it clutter up the menu. A second script (not written, as yet not needed) restores the original functionality. Just a couple of clicks in rox does the job.
I have to repeat this every time an update is downloaded but that is no problem, happens infrequently. I have a script that auto-updates my stuff on every boot.
So I guess this means I retract my request.