School me on radiant zone control

I am trying to learn what I can about zone control, in anticipation of adding new zones to a radiant heating system that had some design 'issues' from the very beginning. I have five zones on my system - four radiant heating zones and one for domestic hot water. One zone goes into a 6-port Caleffi manifold for my basement floor. Another zone goes into a 'plumber-made' two-port manifold for heating two bathrooms on my second floor. The remaining two zones are intended for staple-up tubing on my main floor, which have never been completed or hooked up. I have run out of room on my Wall for any additional manifolds or piping of any kind, and will actually have to install something on the ceiling or on an adjacent wall if I want to use the remaining two zones and if I don't re-plumb the system.

I am trying to figure out if "shrinking" the main heat loop and reducing the number of hard-piped zones, will work in conjunction with a single new manifold and thermal actuators to control the temperature of each circuit (loop?), and thereby give me some room to lay everything out in one place, or I should just completely separate out each zone with its' own circulator pump, mixing valve and manifold? I would leave the basement zone alone, it's working fine. I'd also leave the hot water alone, that's irrelevant. But, can I combine all of the remaining circuits/loops of PEX onto a single manifold? There's a total of five circuits installed (two active, for the upstairs bathrooms) and two more that still need to be stapled up and insulated. That would require a seven-loop manifold and would, in my mind, allow me to use a single circulator pump, a single mixing valve, and a bunch of thermal actuators on the return side of the manifold that would control the loop temp for each loop. It will also significantly reduce the space this system takes up on my basement wall.

Not sure what to do, I have literally been kicking this around for almost ten years, we've never really needed the main floor heat but we're getting older and colder and I have a brand-new wood gasification boiler that will run better under more load. I wish I knew more about how this stuff worked, which is why I am here.

Does anyone have any photos of a compact, cleanly plumbed system that they can direct me to?

Also, on a side note - why would you combine black iron and copper in a heating system?