Well, as the email says this is really between the LMO & the UKG GML.
Your GML says it himself - he holds the UKG to higher standards than the rest of the Legion. To be honest I have no idea how far this can go, and to what latitudes GML's can allow variances.
Perhaps it's best to post on the Legion boards, as it would be interesting to hear from the LC & other GML's why one costume would be held to a different standard than others.
To wit: TIE Pilots troop with weapons all the time, yet there is no film showing them doing so. Same goes with Officers who seem happy to wear what ever side arm they want though only the gantry officer is so shown, and that's with a Power5 and not any other type of blaster.
Again, it all comes back to who has more authority, the LMO or the GML.