Good to see, that you're planning a solid way forward.
Having opted for the Gnome edition years ago because I found myself configuring budgie to feel a little more the Gnome way - the way I was used to, I am happy to move to budgie if Gnome will be discontinued especially since Gnome 4x was apparently developed without a lot of end user involvement, now lacking key 3rd party features. I fully agree with your statement regarding Gnome "...that does not (in our opinion) provide the most optimized experience for laptop and desktop users".
Please provide a migration path for current Gnome edition users.
Make sure you have an application panel like "Dash-to-Dock" in place when you release it and you'll make many current Gnome users happy, I think.
From a marketing perspective, I'd suggest to stop calling budgie a more "traditional" desktop - sounds like "old fashioned" to me which doesn't apply. How about putting attributes like intuitive, lean, modern, efficient, responsive in the foreground to underline its progressive nature.
Add UI step-by-step programming totorials (for low, medium, high skill levels) to the solus webpage so developers find it easy to develop applications based on the new Ecosystem.
Oh, I am sure, I can find a spare SSD to support testing and assume you'll make an announcement, when you need people to support testing.