What 17-inch tires are available (90K-mi, all season, costco)?

I drive a 2006 with 15 inch wheels. I put 90,000 mile (Michilin defender XT) all season tires from Costco on them last year. I like them a lot. Very good in the rain. Fine in the snow. Perfectly adequate the rest of the time. These are fourth set of tires for this car, and best tires I've driven on so far.

I'm shopping for a 2010-2014 model year prius that will likely come with the factory 17-inch rims. When I look up my tire options for the 17-inch rims sold by Costco and others, I'm annoyed by the lack of durable all season tires sold in this size and the costs of 17 inch tires.

Questions:
Are there any Michelin Defender XT (or equivalent) tires made in a close enough size to 215/45R17 that it is compatible? Preferably in a tire sold at Costco.
Is there any reason why a swap for 15-inch rims wouldn't work to have access to normal tires? I assume the rest of the car is exactly the same. this has been discussed before. The 17 and 15 inch stock tires have the same circumference.

 

Well, actually the car started with the integrities. Then a set of Goodyear Triple tread because they were the best rated all season passenger tires. They were crap. Replaced with a set of yokohama. Didn't hold up. Tire dealer didn't honor warranty. So for the next round, I went to Costco for the Defender. I've driven about 35,000 miles on the defender XT, very good. I ultra-commuted between Cleveland and Detroit on these tires. Very good in the rain. Perfectly adequate in the snow (and better than everything else I have driven in the snow)