TS, I do not disagree and I would prefer to have properly trained, kitted out troops ready to immediately dispatch threats immediately if the need is dire enough for this level of security.
This scenario stems from a conversation I was part of at a recent security expo. Several of the companies that currently offer PI services and Armed security services are hiring a group of Joes that get all mall ninja'd out and go sit in the forest calling it an OP. These same Joes are expected to conduct discreet investigations and frankly it is going rather poor in terms of employee comfort.
A chief complaint was the lack of professionalism and general military feel of these security professionals. While the leadership enjoyed the protection and security that these personnel provided it was at a great cost to their image. I do not think that image should ever be a prime consideration if true security is desired.
As I have always loved TR's quote, "An experienced warrior will hold the edge with a 1903 Springfield over a wannabe with a SIG 552." I was curious. Whatever got you in the scenario being irrelevant you have the green light to whack the terrorist scum here in the good ole USA and have to look pretty doing it

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TR, My thinking is similar to yours. I was favoring something like a 10.5" AR with a can on it to preserve hearing inside close confines. I like the looks of the LWRC PDW and it would make a fun little briefcase gun but I am completely unsure of whether or not it is reliable and accurate. Whatever weapon I got would be loaded with RBCD or Lemas if I could get it.
I had thought about just running a plate carrier but the risk of small IEDs such as pipe bombs might make soft armor as well as a helmet similar to OPS CORE with lights nods and ear pro.
As I was thinking about the situation it occurred to me that a breaching tool of some kind would be useful. People will try to barricade themselves wherever and being able to move through non traditional avenues might be beneficial.
As a question TR, what holster would you use to carry while wearing soft armor constantly and add a plate carrier as needed? Would you use the same holster or switch when you donned your PC?