Rebuild the Dev of a non UNIX kernel...

My name for this post may be a bit off but basically I would like to take go though the same proses that kernel developers went though to build other kernels that are based on UNIX such as Linux,
And do it from scratch IE. starting with the base UNIX and building on to it.

So I in theory could make a recipes of sorts to show the development proses in many kernels.

My question is if it would be possible to do this with individual files instead of adding script to the UNIX kernel,
Sort of like the L4Linux project having the kernel built with supplementary files?

Any theoretical thoughts,
Or ideas?