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)

	   o	manipulate an unmounted file system
		   (given a a raw device (or just a file),
		   add/move/remove files)

   Does NetBSD have similar tools (for manipulating a raw ufs)?

Currrently, no, and it's not clear to me that it's worthwhile.

If you're thinking of what I expect you are, you could network boot
and build a file system using native tools.