ECU software development is sort of my day job. If you're going to go down this path, I seriously recommend getting the specialized plugs and connectors and making your own wiring harnesses to whatever size you need. It's absolutely easier than manhandling a full wiring harness or cutting one down. Cheaper, too.
That sorta surprised me. Once I could identify a connector type from a schematic, it was almost never a huge problem getting them in small (1 to 5 piece) quantities. It's mostly a question of finding the right distributor.
