It seems like a lot of possible failure points (multiple pumps, multiple small radiators with lots of barbs) and lots of hassles when the annual (or more often) system flush/cleaning occurs.
Did you consider a single oversized rad/res/pump and then using a panel with disconnects to modularly add PCs? To me that would have been a little more logical because you could put it in a "faux" cabinet on one side and then have easy access to it whenever you needed.
If I ever build a house, it will have separate cooling lines running throughout the house plumbed into it from the beginning and I will just plug into the disconnects when I need to add a PC. I've already sorted it out in my head
