A picture speaks 1000 words:

This great blog entry by Jaroslav Tulach provides most of the info you need for something like the above, coupled with a trip through the NetBeans sources to see how other annotations, such as @ServiceProvider are defined. Together, that should be all you need.
It is by no means finished. For example, the display name should be referenced in the bundle, rather than hardcoded in the annotation. But there are already SO many benefits over the current situation. How about the code completion and Javadoc support for example:

It works exactly as shown, i.e., the above gets me a new menu item and toolbar button, i.e., without writing a single line in my layer file (i.e., I don't need the New Action wizard at all anymore). I plan to write a blog entry describing how I created the above annotation, in the next few days.