But you can go the Smalltalk-style route. You write your app and then use a tool to pare down the environment (kernel included) to just what you use and nothing else.
Indeed. It'll be interesting to see if people use Maxine VM a lot to run Java stuff on a xen/micro-kernel environment.
The HotSpot style C1X optimizing compiler for Maxine is under heavy and constant development right now, I wouldn't be too surprised to see it ready for that sort of thing fairly soon as these things go.