Exotic Khvostov
The two additional features that Arekkz picks out are pretty interesting, the fire rate of the can be effectively be doubled which will unload the clip in nanoseconds but give slightly different perks.
Then there is the ornament slots. This could be absolutely any type of customisation right now as it hasn't been confirmed what happens, however I think it has something to do with the cosmetic features, rather than an additional perk. The concept behing Chroma was a decent one but in reality it doesn't hold much value imo. When there is enough decent armour with an additional shader colour I just don't think its worth the slots of obtaining Chroma and filling the inventory.
I'd love to be completely blown away though if it shows that you can add specific perks to an already buffed exotic. Jury's out me thinks.