If it was me, I don't think I would mess with the main grind. Too well finished, and too much risk of messing up. I grind freehand, so the jig wouldn't come into it...would help with accuracy, but be a pain to use with all the handle.
What I might try is extending the choil. I don't know whether I would be able to get any part of my grinding belt in there, but failing that I might be tempted to try a carbide burr in my Dremel / Wizard type tool. Or a small sanding wheel.
I would think that there would be better support for a finger if the choil/ricasso area was all one height, either way.
Looking at your stuff makes me want to get back to my workshop and get making again! Thanks for posting good stuff