One of the things that I liked about the TOS uniforms - and to an extent the Movies "Monster Maroons" was that the chest insignia gave you an idea a) Which ship the person belonged to and b) gave you more information about what they could do than the TNG-era uniforms (ie a Star means Command, an ellipse in a circle means Sciences, a red cross means Medical (or maybe just Nursing?) a Spiral means Operations)
However, the Spiral is the flawed one, as it seems to embrace Engineering, Security, Communications, Support Services and others (Tactical/Armory appears to be part of Command during the period, another symbol might be good here too). Assuming the Spiral actually represents Engineering - likely as Scotty was the primary character who wore it, what symbol could you have for Comms, Tactical, Security or Services?
To kick things off, I'd say an antenna dish (like in the http://memory-alpha.org/en/wiki/File:Epsilon_IX_station_assignment_patch.png) might be a good one for Communications.
Shamrock Holmes
However, the Spiral is the flawed one, as it seems to embrace Engineering, Security, Communications, Support Services and others (Tactical/Armory appears to be part of Command during the period, another symbol might be good here too). Assuming the Spiral actually represents Engineering - likely as Scotty was the primary character who wore it, what symbol could you have for Comms, Tactical, Security or Services?
To kick things off, I'd say an antenna dish (like in the http://memory-alpha.org/en/wiki/File:Epsilon_IX_station_assignment_patch.png) might be a good one for Communications.
Shamrock Holmes