Hm, I see. The system as it is seems perfectly fine, then. If Admins have to check and moderator new contributors (which IIRC was your main intention), would it be a good idea to open some type of subforum where a new user would introduce themself, or at least, have them show themselves in a way to prove whether or not they're going to do suspicious things in general?
Finally, your belief that you leaving will immediately cause the site to collapse is, for the most part, paranoia as far as I can tell. Unless no other mods/Admins are capable of being on in the same timeframe of you being active, there are a select total of 21 staff capable of working on pages, 30 staff capable of working on threads, and 22 staff capable of being in the chatroom total. Also, if you're only on for 6-8 hours a day at your best, 16-18 hours would then consist of you not being here. And if this place were to go to hell if you were gone, it could last for at least three times the amount of your presence.
You have enough staff to live for some time, the only difficulties that could be present is the reoccuring staff fights and/or something that takes a bit of workaround to solve like say if someone moved a page to a blog page (which is possible), meaning you couldn't undo the action of it being moved, or in other words pseudo-deleting the page.