I have never been part of or responsible for a security team.
I am thinking about one thing though in regards to it.

So just a thought;
There has always been the question of how visible a policing force should be.
One idea is that they should be very visible and the reasoning is that you want their simple presence to be a deterrent to the bad guys and you want them easily found if somebody needs help. It also should be loud enough that they can tell easily if they are in their right positions or not.

Second;
If your church is like any other organization I have ever seen then as soon as you have people designated as some kind of authority they will be expected to act as ushers as well as security guards. You will likely find yourselves expected to act as first aid, as fire marshals and as almost every other service that your churches administrators are wanting but too cheap to contract out for.