Gosh, you shoulda seen the caterwauling the LAST time somebody proposed something that more closely resembled Neighborhood Watch (TIPS). This is having armed persons, acting both under color of authority and with minimal training. Yup, GREAT idea.
Considering a lot of those who are currently nashing their teeth over the abuses against the Constitution would be among those who would volunteer, I'd say your fears of violations in that area are pretty darn small as well.
Actually, given some of the attitudes expressed on FR when now-deceased Freeper matsuidon blew his gasket in Massilon, OH this past summer, I'd say there's PLENTY to worry about. There's (a) what the Constitution actually says, and then there's (b) what somebody THINKS it says, and a for a lot of potential volunteers, there is a significant delta betwixt the two.