Has any dealers offered you this? It's from R.O.A.D. InTire.
Covers the wheels and tires at 100% replacement for any type damage. Price quoted for the 55 was $490.00 for 5 years. Dealer says any Mercedes dealer will handle the claims. I never buy extented warranties but this sounds pretty tempting.
Stock tires are likely to wear out in as litle as 20,000 miles. Is this covered?
No normal wear just road damaged caused by potholes,nails,etc. The guarantee continues on replaced tires.
You also mentioned wheels. If the rims are covered go for it. Otherwise tirerack has replacements for the pzeros under $300 each. How many you think you'll go through in 5 years will point you in the right direction.