I'm with the 'cut the cMP in half' (remove 3.5" drives and optical) camp... add TB3 and/or USB-C, hopefully more PCIe, a dual CPU option (that's upgradable from a single CPU option - direct from Apple)...
I have 8 drives in my main machine. 1 blu-ray writer, 3 SSDs on a switch each with a different OS/config. 4 4TB spinning drives. 1TB only holds about 12 hours of raw 4k video. Why do you still want to see a gimped machine even now? Go buy a 2014 mini.