Glad you're finding the plugin useful and thanks for taking the time to give some feedback.
Your suggestion to add controls to limit the effect to a segment
would be possible, however, I won't be changing the plugin (sorry!). The reasons are as follows:-
1. What you have suggested is very easily achieved by running the plugin on a new layer on top of your image, then deleting the portion you do not need.
a. To select a segment I would draw two straight lines from the centre using the line tool at 1 pixel width, and then 'magic wand' the area to keep, invert the selection and delete.
b. To remove the centre, either use the ellipse/circle select tool or the eraser at a very large width.
I also tend to use a small Gaussian blur after using the effect too.
2. The U.I. (user interface) of the plugin is already huge - I like to give the user as many options as possible, meaning my plugins tend to have more controls than most - if they get any bigger they won't fit on the screen!
Multipage U.I.s are possible if the plugin is created using an advanced program called Visual studio - however I'm too much of a novice to be able to use it. This plugin was one of my first and created with the wonderful 'codelab' plugin.
3. Plugins, ideally, are useful for many users with many different uses for the plugin. Although your ideas would be useful for your use, they would just over complicate the plugin for others (unless I suddenly get 100 post asking for the same thing!). Bespoke plugins are possible though, by using codelab.
4. Life is too short:-
Coding takes time - for me at least.
How many sunrises left? - even optimistically, less than the number of pixels in a 100 by 100 pixel image!
Anyway, keep coming up with ideas and I do recommend you have a go at writing some plugins with codelab.
All the best.