Ask your dealer about a Valet key. They should be able to supply it as I just bought one from my dealer. They did however, refuse to program it. At this point, I have a nice key chain until I get it programmed. Here is my research to date, which I'd ask forum members to correct or update as they see fit. I normally don't like to post until I achieved a solution, but thought I would share my thoughts (I'm surely wrong on many fronts!!)
From what I can gather, there are three components regarding the key. The cut key itself, an immobilizer chip within the key, and lock/unlock buttons that communicate with the alarm. The immobilizer is below the steering wheel under the knee roll. The alarm module is under the back seat.
When you get a new key, you receive a cut key from the manufacturer, but the immobilizer and lock/unlock must be coded to the car. I believe this can be done with earlier cars provided you have the "immobilizer code". I believe this code can be obtained from the factory, although I've been unable to retrieve. According to
@alabbasi, he was able to reprogram a new key for his 2003 Arnage with and Autel MS906 along with the Omitec too. My assumption is you should be able to get the code from the Autel and then use that code to configure the immobilzer within Autel. The alarm would be programmed separately with the Omitec. It does not seem that Omitec supported later cars (2007 or later) as they were supported by VAG, so I'm thinking the alarm would be programmed with that system.
I truly don't think there is any special about our key/immobilizer system, rather the rarity of our cars makes finding anyone to decifer all of this hard to come by. For instance, take a look at our immobilizer (at least in the later Arnages)
Certainly looks a lot like this VW/Skoda unit, a unit that there appear to be many cloning service providers, etc.
With respect to the metal key itself, I simply don't see why ONLY the manufacturer could cut a similar key.
I have access to a friend Autel MS906, but haven't had time yet to mess around. Any other information that can be shared would be awesome as I'd like to have a plan nailed down for Arnage owners present and future.