Maybe parts from the 2013+ models could be used? Or buy a 2015 in good shape.
Through work, I had upgraded to a 6 core i9 2018 MBP at some point.
Advantages: It was a little faster - though not noticeably so for most tasks. It was a little smaller which was nice.
Downsides: Mess of cables+adapters to connect anything. Really stupid, even if you have just 1 USB device, or your iPhone cable etc. They should have left a normal USB port on this machine. Display the same. Battery life the same. Ridiculously expensive. Because I tried to get a significant speedup over my old computer, I got the i9, 32G of RAM and 1TB, and it was > $4,000. But those things don't make a big difference. So for anyone looking to get a new MBP, I recommend the lowest speed i7 (it's only actually ~7% slower, only the names indicate otherwise, check the geekbench results), 16GB and 512GB.
I am now back to my old machine and actually prefer it. It comes with a built-in dock!