I don’t have a problem with that either. I’ve actually supported putting troops on our border with Mexico. This would merely be a spotter service. However, if they spotted cartel members with heavy weapons and drugs, I would support hostile action.
If we're going to do that, we need to give them the tools necessary to be effective (including, as you say, UAS for spotting). At various times we have had coastal artillery, anti-aircraft guns in cities, anti-aircraft missiles around infrastructure ... as long as the militarization is aimed at protecting against foreign invaders, it's well within the limits of what fed.gov should be doing.