Obsidian 1000D - Is a single loop for dual systems possible?

I'm almost ready to buy my water cooling stuff and I have some questions. I have a dual system running in the Obsidian 1000D. One system has a 16 core intel i9 and the other has a 8086k running at 5ghz. Both will eventually have 2080 ti's with a possible 3rd added to the big board for SLI.

Is it possible to do a single loop with dual systems? The problem I'm running into is that if I want to have the main system turned off then the pump will not be running. Is there a way around this dilemma? I thought maybe I could create some type of easy switch.

Another thought I had is could I run dual pumps in a single loop with each system powering one of them. I planned to go with 4 radiators (2 front and 2 up top). I do some crypto mining so things tend to get hot and I might end up going quad gpu's on the main board at some point.

You are looking at 900-1000W for the two CPU/two GPU system. You do not want that in one loop. Your GPUs will keep coolant temp up and limit both CPUs. For your purposes and most others, I would want the CPUs and GPUs on separate loops. It really isn't any different for hardware, just the tube runs. It won't really matter if your GPU coolant is 35 or 45C. That will make a difference on the CPUs and you want to isolate them from the ~650W from two 2080 Ti cards.

Not sure about setting this up to be able to power the main system off. I suppose if you make that a primary goal, put each CPU+GPU in one separate loop, and power each from its own PSU then it would work, but that may not be as important to overall goal of the machine. Maybe the 80W of power saving is worth it to you.