I guess this might be a good idea as it gets rid of the bot problem. However, it requires users to have two accounts (one for the forum another one for the wiki) and also admins that grant the permission after reading the forum. Apart from these points it is a solid way to get rid of the bots.
Another temporary way might be changing all of the "security" questions in place or even the security mechanism at all. Though, I'm not sure how long this will help, if it helps at all.