Basic models could have coil sprung suspension but higher spec cars could have air suspension, don't forget that certain parts of the world though the car would have to run on leaf springs to fit into the pickup category. This applies in certain parts of asia such a Thailand.
Quattro is a must in both manual and automation form. I think engine wise you'd want decent sized diesels not like the 4 cylinders the Merc x class will start off with! So 3.0 v6 tdi, 4.2tdi or at a push petrol wise the 2.9 litre petrol out of the RS4 or similar. or the v8/v10 out of the r8 for the middle eastern markets.
Spec wise sticking with the current formula of se, s line, black edition would work fine I think.
One problem with the Volkswagen pickup is the size of load space and weight it can carry which is less than it's competitors. This I feel would need addressing especially when competing against Mercedes.
Hope IV helped abit and not bored you to death!
Do you work.for Audi by any chance! ;)
Cheers
Steve