&gt; When is the last time you needed a feature that could only be provided by your kernel?<p>Generally these are &quot;unseen&quot; features such as adding multicore support or adding support for a power saving feature on your graphics card.<p>&gt; How are they going to try things out if your OS doesn&#x27;t support any of the techniques they&#x27;re interested in (i.e. novel ways of getting at hardware, novel ways of doing virtual memory, etc)<p>They are interested in a lot more than that. Check the 3L references page for a few examples. [0] Plus you can do many of those things with 3L.<p>&gt; You realize that this sort of thing is a huge area of current research, right? Because it&#x27;s a really, really hard problem?<p>Yes. But it is certainly possible and has already been done to some degree. Genera, for example, did it and a number of other real-world and research OSes have done it. Of course the real challenge is making it as real-time as possible but getting it most of the way there isn&#x27;t actually that difficult.<p>[0] <a href="http:&#x2F;&#x2F;3lproject.org&#x2F;references" rel="nofollow">http:&#x2F;&#x2F;3lproject.org&#x2F;references</a>