I just got the Mk XI set on my KDF Alien, after equipping it and selecting the Omega option in the drop down the uniform's available but one of the options is available. Both of my Federation characters also have the Mk XI Omega set and the option missing is available for both of them, my Orion doesn't yet have one so I'm not sure if it affects anything but the Alien character on the KDF.
The tailor gives the option to equip everything my Federation characters can except for the right wrist attachments which isn't listed. It's not on the character either;
Although it is present on the arm which the option's available for;