This sounds like a great idea. Perhaps two versions would be good...
1) On one end, the male and female stack and the other, just the conductors.... so you could connect it to a bread board or whatever else you wanted to do... (power supply, or sensors, or whatever)
2) Put the stacking cable on both ends to join two stacks.
Make both options available in different lengths.
I don't know if this is too much to ask, but in option 1, make it easy to exclude certain lines... be able to clip them or something.