Sorry, not a good idea. Never try to get the better of the host on his/her own program. The host is in control. And this host wants to make the Sarah threat go away, you know she does, and will do what it takes.
You raise a great point. Also, Oprah has an audience, which brings up a very uncontrollable element. They could be supportive. But, they could also be somewhat hostile, or worse, indifferent. I said up-thread that I don't believe Oprah will be tough - but, I could be wrong.
This will be an interview with tremendous potential upside for Palin, and will also pose some perilous downside as well. It will be the most viewed, most talked about interview since Nixon/Frost - of that, I have no doubt.