It might be a weird idea in 2015 but I'd be curious if it would be helpful for consoles to have DOS-like operating systems. In DOS you were provided all the basic OS services and drivers you need for a typical application of that era, but you also had the possibility to bypass the OS completely and talk directly to the hardware if you really wanted to, and your program ran in kernel mode and ruled over the system. Since the hardware is always the same there would be only one I/O interface to code against per console. (So it wouldn't be like the actual DOS from the early 90s where you had to code for all possible drivers.)
I don't think console manufacturers would go in that direction with modern consoles though, for several reasons.
- Next-gen graphics API like Vulkan and DirectX12 are already doing a great job at removing as much overhead as possible from the driver by moving a lot of responsibilities to the application, and they do so in a safe way that doesn't expose dangerous kernel-mode instructions. It would take away the overhead of the syscall (context switching, reading interrupt vector, etc), but that's about it.
- It would limit the manufacturer's ability to improve their console's performance by providing better drivers if some studios are bypassing their drivers.
- It would be dangerous for the manufacturer's precious DRM. A buffer overflow happens quickly, and it's quite useful when it's running in kernel mode. Find one game with a buffer overflow and then you can probably rootkit the OS with a DRM bypass and then it's game over.
- Since games and saves are all on the harddrive a fault in the code of one game could affect more than that game itself. For example, if a game breaks the file system, it would break a lot more than itself. That's a big risk that neither the developer nor the console manufacturer might want to take. Besides, only the brave would play Bethesda games.
- Privileged code is inherently more difficult to debug. Even your debug printout and code dump functions can get corrupted if something goes wrong.
So yeah, console games are probably going to stay in user mode for now, and run huge OSes. But as a PC gamer this is a good thing because I don't want developers to get too comfortable with kernel-mode tricks, otherwise I'll get less games to play.