For what it's worth, there are already other exceptions. For example, you can use (non-deadly) force to detain other persons if you reasonably believe you have witnessed them commit a felony or certain misdemeanors, as long as the force used is necessary and reasonable (possibly matching the force used by the offender to commit the felony, or sufficient to restrain the offender) under the circumstances. You generally have the same duties in an arrest as an officer of the law, but with less protection from potential prosecution.

Civil search of property is, in my opinion, a less serious power/responsibility than citizen's arrest; though I guess it could apply in more circumstances.