Create Change implementations to add or update an Annotation on a package/class/method/field ...

I'm currently working on PDE to convert a project with a refactoring from "old" style MANIFEST-First to using bnd instructions/ OSGi annotations here:
- https://github.com/eclipse-pde/eclipse.pde/pull/934

I now came across the need to modify a CU by adding an annotation to package/class/method/field but it seems there is no method for that currently, for example I found this post on stackoverflow:

- https://stackoverflow.com/questions/12748308/attach-annotation-to-class-with-jdt

also this example of course does not cover the case that the annotation is already there an needs to be updated.

As it seems to be a non trivial case, I wonder if it would be possible to add some predefined `Change` implementations to JDT from the JDT experts so they can be reused by other implementations. For my purpose even something in the internal refactoring packages would be sufficient.