This is my plan as well, start with the chassis and find a newer mainboard second-hand. I configured a 2TB SSD and 64 GB of LPCAMM2 RAM to see the price for the new 13 pro and it was doubled from about 1500 CAD to over 3200 CAD before tax. Upgrading the mainboard, when I have a perfectly functioning (and fast) 12th gen Intel i5, is out of the question for now.