Imported rule-sets ".prule" files IMO would be safer as a "Staff Settings..." property.
Separate and independent of notes, rests and other objects that can be deleted.
Or better yet_
Rule-sets attached to a staff should be "ignored" by a "Delete" or "Clear" action unless added to the "Clear Special" action.

Also, combining the _Use Rules... and _ Use Instrument... dialog boxes into one would IMO cleanup and better localize the associated tasks.

,Johnny