Yes you can do that. But unfortunately you can't then use the on mouse out action to set it back to allowing the commands to interact with both objects & characters as it reacts as mouse out as soon as you activate it & you end up with the mouse cursor / action text toggling on & off.
The problem this generates is when should you reactivate the command to interact with both objects & characters as we've just established that when only objects are allowed, everything but objects will be classed as empty, which means that you'd either have to add a timer or possibly make it so that it resets on hover over an object but that means that all characters will be inaccessible until you hover over an object.
In other words: I'm not sure how to broach this issue at this moment in time.
Maybe the devs could add a boolean option to the characters properties tab to determine if the mouse should detect the characters? I'll make a note of it on the dev tracker.