I also think that re-introducing security questions could be a good thing. Granted, it isn't perfect, but does it have to be?
A lot of people seem to get hijacked through their email. Jagex doesn't ask anything other than having access to it. Jagex could ask to answer a security question before sending the email.
Many services still use recovery questions. There has to be a reason why. Most seem to use them in the way I described, but I could be wrong.
As for the previously mentioned problems, there has to be a way to mitigate most of that, right? Jagex could allow us to change them when our account has been in "good standing" for 12+ months. Or when Jagex determined that an account has been hijacked.
Just a thought...