The add-on manager doesn't work for plugins. These are only registered when Gimp starts. No too hard to make them distinct:
- Change the "group_chfont" (first line after "register(")
- Change the "Change font..." to describe the behavior better
- Select layers with the link icon (it is easy to link everything in two clicks). Linking a group would mean to act on all text layers it contains (with subgroups if recursive).
- Optionally correct the layer position. Gimp keeps the position of the top left corner of the layer, but in many cases you would like to keep the center of the layer at the same place (or some other corner)
- For the option above, use either the layer boundary, or a tight-fit rectangle around the text.
- Other options (spacing, alignment, hinting) are not availabe in the API...