I'm so happy to see other builders here building big and ambitious projects. For me, this the heart of BYOAC. In times past 'experts' would have weighed in and maybe told you rotating a CRT is too tricky/don't bother/ blah blah blah. Your ring bearing solution is really good! All that weight nicely supported and balanced allowing for quality rotation control. The main issue with lovely old CRTs other than weight, is image issues being affected by tube orientation changes. If you can solve magnetic coloration issues this will be epic indeed! When building your own arcade cabinet CRTs are still king for the real arcade experience.
I've been working with MDF for a long time. I love it for cabinet building but it has its own best practice rules. Grain free, shapes well, great for gluing panels and takes surface finishes (the right ones) like a dream. It also has terrible dust issues, is heavy, splits when nailed or screwed in the wrong way, dulls tool blades, absorbs moisture and yes, bends in the sun
. I often combine it with Marine Ply to solve some of those problems.
Watching your progress