Maybe I'm missing something here, but... if the panic here is about "How do I get software onto HFS disk images for vMac when Snow Leopard won't write to HFS disk images anymore", isn't the simplest solution to just use BasiliskII or Sheepshaver as a go-between?
Both of those emulators create a virtual drive through which one can read the host computer's UNIX filesystem. They use the same disk image format as vMac so it's not exactly challenging to fire up one of them with your for-vMac disk image mounted as a second drive and use it to copy the software from the host system over. (As a bonus, BasiliskII/Sheepshaver are much faster than and can run newer programs then vMac, so if you're dealing with .sit, .hqx, or other archive formats as a go-between it's easier to work with them then inside vMac.)
The "dd" trick is the standard way to get a bit-exact copy of a disk under UNIX. I guess I just don't see how widely useful it's going to be under these circumstances. It does work (I've done it) to make images of 1.44MB floppies, but "old" Mac software is probably going to be on 800k disks and I don't think *any* USB drives will read those. If you'll be needing to have an old Mac around to read disks anyway you can just use Disk Copy and be done with it. If you're packing up a larger disk you're probably better off using an archive format and transferring the archive file. (Which then can be made back into a disk using BasiliskII/Sheepshaver as described above.)
Another option, in theory, is that you might be able to point Basilisk directly at your hard disk/zip drive. See this page here, the part about HFS volumes. Again, I've done this under Linux (read a Mac-formatted drive hanging off a SCSI controller), but in principle it might work under OS X as well. (Similar to how you figured out the mount point to "dd" from in your instructions you'd use that as the target for setting up your volume in the Basilisk dialog box. You'll probably have to run Basilisk as root or set the executable SUID root for this to work. Again, whether it does under OS X I can't say.) I guess that's no more friendly then "dd"-ing a copy and mounting that as a disk image, but if you just want to get a subset of files off a very large disk and move them to images it might be a useful technique.
I guess I just don't see the panic angle because almost all the time I've been running Mac emulators it's been on host OSes that never had native HFS support in the first place. The tools to get by without it are certainly "there".
Both of those emulators create a virtual drive through which one can read the host computer's UNIX filesystem. They use the same disk image format as vMac so it's not exactly challenging to fire up one of them with your for-vMac disk image mounted as a second drive and use it to copy the software from the host system over. (As a bonus, BasiliskII/Sheepshaver are much faster than and can run newer programs then vMac, so if you're dealing with .sit, .hqx, or other archive formats as a go-between it's easier to work with them then inside vMac.)
The "dd" trick is the standard way to get a bit-exact copy of a disk under UNIX. I guess I just don't see how widely useful it's going to be under these circumstances. It does work (I've done it) to make images of 1.44MB floppies, but "old" Mac software is probably going to be on 800k disks and I don't think *any* USB drives will read those. If you'll be needing to have an old Mac around to read disks anyway you can just use Disk Copy and be done with it. If you're packing up a larger disk you're probably better off using an archive format and transferring the archive file. (Which then can be made back into a disk using BasiliskII/Sheepshaver as described above.)
Another option, in theory, is that you might be able to point Basilisk directly at your hard disk/zip drive. See this page here, the part about HFS volumes. Again, I've done this under Linux (read a Mac-formatted drive hanging off a SCSI controller), but in principle it might work under OS X as well. (Similar to how you figured out the mount point to "dd" from in your instructions you'd use that as the target for setting up your volume in the Basilisk dialog box. You'll probably have to run Basilisk as root or set the executable SUID root for this to work. Again, whether it does under OS X I can't say.) I guess that's no more friendly then "dd"-ing a copy and mounting that as a disk image, but if you just want to get a subset of files off a very large disk and move them to images it might be a useful technique.
I guess I just don't see the panic angle because almost all the time I've been running Mac emulators it's been on host OSes that never had native HFS support in the first place. The tools to get by without it are certainly "there".