Possible to Add “blocking” Key to Exec Action?

At the moment, long-running exec actions for which repeat is True continue executing even after the user is allowed to start interacting with a sandbox. Might it make sense to add, e.g., a blocking attribute that, if True, prevents the user from interacting with the sandbox until the action has completed? This way, longish-running commands like apt and pip could be allowed to finish before the user tries to interact with any such installed software?