I found a neat way to get LOS 1.2 installed on my external ProFile drive that may be helpful for someone. Note that I used a Lisa 2/10 for this process.
You'll need a Lisa 2/10 with an internal X/ProFile, as well as the LOS 3.1 and 1.2 CF cards from VintageMicros, and a 3.5" floppy with BLU 0.9.
1. Install the Parallel Expansion Card (if you don't already have one installed).
2. Attach external ProFile drive(s) to the expansion card port(s). Switch them on.
3. Boot the Lisa 2/10 into LOS 3.1 from the internal X/ProFile. (Just use the LOS 3.1 CF card that comes with the X/ProFile.)
4. After the Lisa boots, the ProFiles will complete their self-test and show a steady red "Ready" LED. They will not mount on the LOS desktop until the next boot, so reboot the Lisa.
5. After rebooting, LOS will prompt you to format the ProFile(s) (if not previously formatted). Go ahead and do that. Note: This may not be necessary, but I did it anyway. LOS will subsequently mount the drive(s) on the desktop.
6. Open Preferences and set the Lisa to boot from the floppy drive.
7. Power off the Lisa.
8. Insert BLU floppy disk.
9. Remove the LOS 3.1 CF card and insert the LOS 1.2 (or 1.0) CF card. In my case, both cards were STAR Mode = 3 / Target = 0 cards. I did not have to change the settings on the X/ProFile. I'm not sure if that matters.
10. Power on the Lisa.
11. BLU will boot as usual. Use the hard disk function to copy disk to disk, i.e. from the internal parallel port to the appropriate external upper or lower parallel port.
Done. In my case, I have a Lisa 2/5 that has been modified with the R41 and R47 resistors and the appropriate CPU and IO ROMs to create a Lisa 1. Hooked up the newly created LOS 1.2 ProFile to its built-in parallel port and boom! Lisa Office System 1.2 booting on an attached ProFile drive.
Hopefully this helps someone trying to achieve a similar result.