If you have photoshop or another equally powerful image editing program then it would be easy to just create a multi-layered template.
using the regent patch you posted up for example layers would be:
1) the white circles surrounding the outer section of the patch
2) a layer with the gold circles
3) a layer with the red circle
4) The curved text layer
5) Several layers for the different aspects of the center of the patch.
If you used these layers to create a template then you could easily edit every aspect of the patch without having to redo it from scratch every time. Just make sure you work from a copy of the template so you don't accidentally save over it. And added step that isn't done with that patch, is after you flatten all the layers you could then use one of the effects to make it look like actual fabric. If you desire the physical patch appearance over a computerized logo patch appearance.
If he's doing it as an SVG in Illustrator, then Inkscape would work for us as well. Plus, unlike Illustrator, Inkscape doesn't cost an arm, a leg, and 100,000 Dilithium. Its my default image editing software at work, though it sees more use as a "turn PDF into image" software than an actual image editor.
The opinions expressed in my posts are not necessarily those of my employer or Subspace Radio.
PS: My show is actually at 0200 GMT these days. I really need to dig up the PSD for that signature and redo it.