I think the Elegance was a mix between the CD and the CDX, I've seen Elegances without leather, without nav, with telephone (2015) but without CID... so, if the buyer didn't add any toys when buying the car from the dealer, i think the Elegance was like your CD. The most you add, the most you "CDX" your Omega..
Our Elite was called Executive but with some differences... it's a mess.. only sold with 3.2 engine, not all the Executives had sunroof and all your Elites have it.. so if you wanted a full equiped 2.6, like your Elites, you had to buy an Elegance and charge it with all the toys, there was not a 2.6 Executive like your 2.6 Elite.
Here the facelifts were only sold under 3 spec levels, Sport, Elegance and Executive. I've seen omegas imported from Germany badged as "special edition" with grooved seats and "greenish" black leather..
I think they are two different ways of selling cars... i may be wrong, but in UK, if you bought a new Elite, you didn't add extra equiment cos the car came with all the possible equipment, here you could buy an Executive without sunroof, if you wanted it, you had to order the car to factory with the charge of the sunroof... So, you could buy the lower spec one and start adding equipment.. and you could also buy the highest specs one but it came with less or different toys than your Elites.
Prefacelifts 3.0 for example, were only sold under MV6 badge, but they hadn't sport seats or leather, you had to add it from factory. 2.0 16v were only GLS... 2.5 only CDX IIRC
