This is a fine idea, but I think it should be disabled by default (i.e. if someone adds those lines of code, it works… but in using the NewPage module those lines are by default not shown)
Reason — I want to make editing pages as simple as possible for new wikidot users on my website. If they see metadata at the top they might accidentally change it and cause problems. Experienced users that know how to modify meta data can still do so, just by typing in a few extra lines! :)
Then again, you've mentioned that only administrators and moderators will be able to "view" and "edit" meta data.
If the page source contains [[meta]] … [[/meta]], how will it deal with a regular user clicking 'edit' ? Will it simply show the rest of the source, but hide anything within meta tags ???