Thanks, guys. We were thinking of the tunic you see McCoy wear in ST:TWOK. It's basically where he took his maroon jacket off. It had no insignia. We opted to go for that look originally, but had enough feedback to add the delta back on. After our seventh production, "The Engineer's New Clothes," we switched to a mock turtleneck and added the delta.
The pin on his neck is his rank pin. The communicators are hand held devices, but our pants have pockets they are generally put into. We made a few creative changes like this since we're in the post-TOS movie era. Who's to say Starfleet didn't add pockets back in for a while?