Wow. Do you realize the last person to do this alone took over 4 year to get to his own version 0.3.7 (AtheOS)...and that was 10 years ago? The amount of new hardware and variations of drivers is way over 100x more. Do you truly realize the work you would have to do?

If you want performance, you will have to write in assembly. C is simply not low-level enough to keep your resources clean.

And, just because you include the Linux core doesn't mean your desktop has to look like Linux. So, that could still be an option. Or, you can build off of the UNIX core.