There is nothing wrong with a believer posing honest questions about anything.
I suppose that non-Christians may ask about a lot of things. I don't usually get questions about Noah's Ark, or Jonah. Eventually, I'd like to get an answer that's better than, it was a really big boat and it took 100 years to build it.
But what I've found is that if non-Christians are interested in Christianity, they are usually more interested in what belief in Jesus does for a person, how it improves their life, how it improves their character, etc.
Regarding being a "devil's advocate", I think it can be harmful to non-Christians to know about some of the garbage that goes on in churches, such as adultery, embezzlement, child molestation. So it goes with questions that the Christian does not need to pose to the non-Christian. I don't point out contradictions in Scripture even though I know where they are. If I non-Christian says to me, "Isn't the Bible full of contradictions?", I won't show him the location of the contradiction. Instead, I'll just ask, "Can you show me one?" Chances are, they can't. If they can, then I'll answer their question, if I am able to, and if not, I'll look it up and get back to them.
Still, I haven't ever been able to adequately answer for myself the question of Noah's Ark. With Jonah, I can say, well, he got swallowed and thrown up by a fish. Ok, that's possible.
But Noah's Ark is a really tough one for me. It's important to me, but not the most important thing.
AJ