Was that computing, or aeronautics or...
I would take a guess that profit margins and product reliability are somewhat better in aeronautics....
Resellers pretty much give away PCs / Laptops these days, unless you're doing significant volumes you'll be lucky to make £10 on a £2000 laptop ! Manage a clean 5% margin and you're doing well !
There must be a pick off point to supply LEDs. The old ones were build into the drive itself. Anyone remember if the signal came off the controller or the drive circuitry?
Perfectly viable, the little disk duplication box I've got on my desk has a light that flashes when data is being copied.
You just need to pick up the right signal off the cable, probably no coding involved, just pure electronics.
For a PC building guru like you it should be a piece of cake .....