So, my friend had a cracked iPhone 5c, and I ordered the basic screen replacement kit. When I got to the point of removing the front camera and sensor cable from the old one, I apparently didn't hold my heat gun on it long enough, because the presence sensor didn't come out with the ribbon cable. I ordered a replacement cable from eBay, but when I put that in, the front camera and earpiece no longer worked, as well as the presence sensor. At this point, I went and ordered the replacement cable from iFixit.
It went pretty smoothly, until I had to reattach the ribbon cable to the mainboard; for some reason, it just wouldn't line-up properly. I had to have my friend hole the screen while I used both hands to move the cable into place, a process that took just as long as the rest of the repair. But once I got it in place, it worked perfectly.
The original part had a small piece of foam on the back of the mainboard connector, making it easier to line it up. Maybe you could include that in your replacement parts?