Minor NIT:

     some OS's have portable tools that allow:
  
  	   o	building of populated file systems
  		   (given a template construct a non empty filesystem
  		    possibly as a simple file)
  
     Does NetBSD have similar tools (for manipulating a raw ufs)?
  
  Currrently, no, and it's not clear to me that it's worthwhile.

Ummm while its true you can't manipulate a raw ufs, you CAN mount a file
in UFS space as a filesystem, and write into it a filesystem. This is how
the boot images are constructed. These files can then be written at least
to /dev/fd as a bytestream, to cause it to behave as a valid FS because
Many of us have mounted them eg to replace a kernel image on the boot.fs
disk.

If you have NetBSD sources scripts & makefiles for this is all under 
/usr/src/distrib.

In short you don't need to make boot.fs disks on a box with a real live floppy.

-George