We at Travel-SE have a lot of tags, by virtue of the topic. For example, there are a large number of airport tags (with standardized, though somewhat uninformative names), and wikis for new tags are rarely added, mostly because one has to either come up with a good excerpt/wiki on the fly (always different and often lacking important info), or hunt for a template from an existing tag.
Either way, it's an effort few feel the need to do, but in the case of airport tags, the tag wikis are almost mandatory to figure out what the tag represents. Popular tags do get their wikis eventually, but for a long-tail tag system such as the one Travel-SE has, the less obscure tags are precisely those that wikis.
So, the suggestion:
- Templates can be added and changed in the same way custom close reasons are treated -- by moderators only. The requirement for approval from another moderator can be possibly removed.
- Moderators (and possibly trusted users or users with sufficient rep to edit tag wikis) pick manually a tag template from the list when editing tag information.
- Tag templates can either be globally allowed, or only for certain regexp-ed tag names.
There probably won't be more than a few templates necessary per SE site.
I'm certain other SE sites will benefit from a templating mechanism for their tag wikis, and some probably have standardized internally a template for certain tags. A central template mechanism will make this process way easier.