. . . I have never understood why the units couldn't just loan a few junior enlisted to man the gates on a rotating schedule (even with deployments)....
That will work if you only want these junior ennlisted soldiers to check ID cards.
The Army published/updated a regulation about what a facility "guards" supposed to do, quite extensive and different levels of training requirements.
I remember seeing juinor enlisted soldiers and sailors, acting as gate guards at Fort Mead after the 911. I think they were only trainined to check ID guards.
What do you do, if the ID card is fake, what do you do if the license tag is expired, what do you do if the driver pulls out a gun?
If we want folks to perform access control only, yeah junior enlisted soldiers on the gate checking ID cards will work, but if we want some security no.