@DownPW this is a great response, and it sounds very much like you’ve thought things though. I agree - it makes more sense to cease development of the v2 theming engine, and focus on v3.
However, it’s worth noting that v3 (particularly with Harmony if I understood correctly) will also have the capability of switching themes - or at least, colour swatches, which is where I was originally heading with v2. It will be interesting to see how this materialises over time, given that the version in Persona seems to be something of an afterthought that doesn’t work very well either.
The new Swatch capabilities skates for inclusion into Harmony may well render the custom theme switcher we developed obsolete if it offers a hook meaning it can be extended.
From my perspective, all of my custom scripts will be updated to work with, and be fully supported in, v3. This is inclusive of the theme switcher (if applicable) and the custom footer etc.