I'm not sure how much RPi can handle - can you test my other theme NEVATO to check if it is working on RPi?
You can download it here - www.onyxarcade.com/nevato
It also has a flat structure (no subdirectories) - I wonder if it helps with zipped/unziped theme problem.
I have tested NEVATO. It works great with SQ lower quality videos from emumovies and screenshots.
I also tested FlatBlue with just screenshots and no videos. It does not seem to make much of a difference in the speed. I am not an attract mode advanced user but I do see a bunch of errors from attract mode saying assets are missing when loading the theme as well.
It's to bad as this theme would be a game changer for the PI3. Even with just screenshots I prefer it over anything else. It's very elegant and well done. Great Job!
I am more into consoles then arcade stuff and Flatblue or your other one velvet seem like perfect fits. I would love to help beta test Velvet as well on the pi3.
I wonder if it's not to much to ask, even some slight layout tweaks would be awesome for the PI:
Making the left side bar wider, and increasing the font size and the menu snap size. The reason is, a lot of the emumoves and snapshot/video preview art floating around is low quality 240p or 480p. If you enlarged the sidebar like it is in velvet, this would let the menu snaps/icons shine which look good on 1080p displays at that size or a little larger.
This would also make the right side video/snap preview smaller, making it look better on 1080p screens as you would not be stretching the already low quality 420p/240p video, like it is in the velvet previews. As the fonts and theme assets scale well I would think, but the rom art movies/snaps do not seem to. So these small tweaks would still keep the elegant design while hiding the art quality at the same time.
So it would effectively be like finessing a similar look you are getting from your arcade cabs where the design is more narrow, but it's designed for a wide 16:9 1080p television. So the column ratios would be similar.