When writing an example question, often the writer of that question has a good idea whether or not he considers the question he's writing to be a good example of the kind of questions he'd expect for the site. Therefore it would be great if the original author could vote on his own example questions just like any other user.
I think this makes a lot of sense. Area 51 proposals are not stackexchange questions. The "asker" is not neccessary biased towards their question as they are towards their answers on other sites.
Area 51 encourages you to have good and bad examples of questions. Right now I would fear that someone would mistake my planned-bad question for a good one, and it would start to get upvotes.
As a workaround, I would probably just leave a comment under my question saying it is a negative example.
As a permanent solution, I suggest you can either vote on your own questions, or better: Your question starts out with either +1 or -1, and everyone can write five good questions and five bad ones (instead of 5 "neutral" ones).