NetBSD file system chat

Would anyone like to join in a discussion on implementing a new file 
system for NetBSD with huge file system support (> 3TB) and journaling? 
  I know soft updates on BSD systems do work like journaling, but I'm 
not knowledgeable enough to say if one or the other is superior under 
certain circumstances.  Can someone comment on this?

Since we can't know the physical disk geometry on modern disks, it 
doesn't make a lot of sense to design a file system with knowledge of 
cylinder boundaries or any other disk information.  A new file system 
should probably be a simple layout of extents of size x (probably page 
size, and configurable at file system creation time).

Can a new file system somehow be implemented in userland first before 
adding it into a kernel?

--
James