Hiding built-in scratch categories?

[DT-is-not-available]

Is there a way to (using an unsandboxed extension) hide/disable block categories from the toolbox? I have been searching through the scripts and the Scratch.vm object for some time now and am unable to find a way to do this.

[GarboMuffin]

Why do you want to do that?

[DT-is-not-available]

I'm experimenting with making an extension that changes the display output to something other than the scratch stage, and still having the default motion/looks blocks available wouldn't quite make sense.

[GarboMuffin]

make the extension first, then discussion about those categories can happen