Got my hands on a Dell Latitude ON module. Turns out it’s nothing more than a 2 GB flash module that fits in a mPCIe slot and is wired to the USB lanes. Shows up as /dev/sdb.
I do have a couple of old laptops that don’t have a secondary SATA drive slot, but do have open mPCIe slots with USB lanes (no mSATA lanes). The Latitude ON module would allow for a dual drive system, albeit a rather crappy one. What would you put on a secondary internal drive if it were limited to 2 GB and USB protocol?
Swap partition?
Swap would probably destroy that thing. And be unbearably slow.
I agree with the others, a rescue partition type thing is probably the best option.