Obviously there would be a need to identify incoming ships and aircraft for threat assessment. The USS Cole indident comes to mind here. Don’t think that a milita, or at least my concept of one, quite fits this need.
This presumes we have all the equipment to detect threats and react to them, with trained forces. If ALL eligible persons are trained, then it becomes more of a moot point. Still need detection and identification systems, as well as a PA and other communications, armament and trained personnel
Never be afraid to try something new…
Remember, amateurs built the ark, professionals built the Titanic.
Depending on the size of the community I would say an armed populous would be a great deterant. Then add on I would have voted in ‘constables’ for policing type work, threat detection, and emergency command. (All other decisions would be made by popular vote in my vision). Require everyone to have some minor training in gun use, and what to do in X emergency, and you’d probably be safe enough. If bigger, I’d still go with a public police force. But any police officer can be fired by popular vote, since it is a public possition. No matter the size I think patrols and the like may be a bit extream. If someone wanted to get at you that much, you’d probably already know it, and either call for international support, or arm yourself appropriatly and START patrols by the residents.
I would do both: have every adult armed and trained, and also have community defense sensors and resources and some personnel dedicated especially to monitoring external security.
This happens to be the Swiss model in essence: every adult male within an age range is armed and in the militia, but there is also a professional officer corps that does training and provides structure and guidance in the event of invasion.