"I was hoping Arc would be powerful enough to do this."
OK, asbestos did not work, try the foam!
What you might be missing is that power makes attacks easier, not harder. As I suggested, part of that power is reflection so you have a fighting chance, my concern is that once you have blocked all the exits there will be no way to get in. Whatever that means.
"you agree this would be very useful"
I do? Wow. Actually, I do not know much about security,tho I might have to learn soon. My guess is that probably the best way to go is not to cripple the plugin, rather to allow only registered, vetted, digitally signed code to run. ie, the plugin looks for a digital certificate before launching.
Tilton's Law: Solve the right problem. What is the problem? Losers posting evil code. Solution? Don't run just anyone's code.