OS Language Choice
C is by far the single largest source of security holes in software history, so it's out more or less automatically by default. I'm sure that causes many C developers to sneer at the very thought of a non-C-based operating system, but the unavoidable cost of fixing the large numbers of bugs and security holes that are inevitable for a large C project is simply more than can be borne by a small team. There is much else to do besides writing code here, and C hooks can be generated wherever deemed necessary as well.
C++ is the best candidate for me personally, since it's the language I know best (I also know C too). It's also basically as low level as C but with far better abstractions and much better type-checking. And just like C, you can inline Assembler code wherever needed in C++. Although poorly-written C++ can be as bad as C code in terms of safety due to the necessity of it being compatible with C, it also has many facilities to not go there for the sane coder who adheres to simple, tried-and-true guidelines. There is also a good C++ project already ongoing that could be used for a clustered unikernel OS approach for speed and safety. This approach could save drastic amounts of time for many reasons, not the least of which is tightly constrained debugging. Every 'process' is literally it's own single-threaded kernel, and mountains of old-style cruft (and thinking) typical with OS development simply vanishes.
FORTRAN is a very well-established language for the sciences, but a) there aren't a lot of FORTRAN coders, and b) it's probably not the greatest at being a general-purpose language anyway. I'm sure it could be made to run robotics hardware, but would probably be a challenge to turn into an OS.
There are plenty of dujour SJW & coffee languages out there, but quite apart from the rampant faggotry & SJWtardism plainly evident in most of their communities, none of them have the kind of industrial experience and pure backbone that C, C++, or FORTRAN have.
D and Ada are special cases and possibly bear due consideration in some year's time, but for now C++ is the obvious choice to me for a Robowaifu OS foundation, Python probably being the best scripting language for it.