That... Shouldn’t be terribly difficult? Though I don’t believe UEFI has sound drivers (you’ll have problems writing one yourself because even frickin’ sound-codec chips have NDA-only datasheets these days), and the stupidest thing is that the “graphics output protocol” doesn’t indicate vsync so you can’t do tear-free blitting, which is literally worse than VGA.

Well… UEFI is kind of modern DOS.

That honestly sounds amazing. Imagine booting into something like a grub menu that's just a list of classic games.

Welcome to Amiga games, in many cases the floppy would contain the boot loader that would directly jump into the game.

At least on the Amiga 500 you would not go through the trouble to start Workbench, only to load the game, unless you were a lucky owner of an external hard drive.