Very nice Marc! I'd love to see mosaic once it's done. If this teaser is anything to go by it'll be epic
Bayer Drizzle certainly does help, I've got a 3x3 bayer drizzle going right now! I wouldn't generally recommend a 3x3 though, apart from needing at least 50 frames to get good sampling (otherwise it can leave some nasty things) I'm doing it purely to fix up some star shapes.
I've found that even if your sampling is pretty good, thinking here of using your QHY8 with CN-212 or 8" F/4, bayer drizzle at 1x1 sampling still helps improve things from just a standard stack. It doesn't increase resolution but helps give a more natural placement of colour and should (in theory) give a more accurate PSF and be closer to what a monochrome sensor would in RGB images.