As I anticipate needing to backup the NAND repeatedly as updates are applied, I've been thinking of ways of leaving the wires connected permanently but with a way to disconnect the lead going to the LPT.
My original plan was to use a 15-pin D-Sub socket fixed to the back of the case, with a 15-pin plug joined to the end of the LPT cable, but I'm put off by having to cut a hole to mount the socket, which would require removing the motherboard to ensure I don't short anything with metal filings.
What I'm planning on doing now is using a PS/2 socket, which has 6 pins plus the outer metal body so making the required 7 connections, wired to the motherboard and then a PS/2 plug on the end of the LPT cable. This is a lot simpler as there's a hole in the back of the case through which I can poke the cable attached to the PS/2 socket (I butchered an extension cable so I've got two molded connectors each with a short length of cable attached), leaving the socket outside the case.
My only concern is whether it's safe to have the outer metal body, which will be connected to GND (J1D2.6 or J2B1.12), exposed. I can always wrap a bit of insulating tape around it when it's not in use, but it would be good to know whether that's necessary or not.