I have a 2005 CL 600 bi turbo,also with full history. The local MB Dealer offered to purchase mine and said it would be put on the forecourt. I think condition and history count as much as age. I purchased it in 2011 with 12 months tier 1 warranty. I renewed the tier 1 for £1308.60 after 12 months, they will cover the car up to 100000miles (at a cost). The tier 1 is what you get with an approved used Mercedes. It may be worth doing this and putting the cost on the price of the car. People would probably purchase with the peace of mind that comes with a top notch warranty.
And yes, the warranty is transferable.
And yes, the warranty is transferable.