Truth on the kernel. I'm used to working in an environment where we own the OS, the board design, and the design of many of the chips ... which means we can make it do whatever we need (downside is, you have to maintain it all too). However, our needs are unique enough to justify it -- computing is hard in an environment where atmospheric radiation can flip random bits for you (See: https://en.wikipedia.org/wiki/Single_event_upset).
