Filing an extension of a none immigrant status for the ultimate purpose of filing AOS is possible and legal. There are previous DV selectees who have done the exact same thing. However as long as you're aware an approval of the extension is not guaranteed, and if that petition gets denied while your AOS petition is pending, you're automatically no longer eligible for AOS. Your AOS petition will most likely get denied also. Now, that you've been adequately informed (I think?), you decide on the best course of action for your case.