I cannot claim any "experience" making super routers, but I have made a few tables and converted a couple of milling machines. But enough of the X, here are my thoughts on the Z.
With a knee mill you have 2 controls for the Z, you can lift the table of lower the quill. A round column mill is similarly adjustable. When you CNC it you probably motorise the quill and use the other, heavy duty adjustment, to optimise the quill travel and get maximum support on a job by job basis. You would be lost without this double control of the Z and yet nobody puts it in a home build.
I suggest you make the entire gantry moveable in the Z with some big bolts so you can lock it in the optimum position. I do have expertise in this because when the locking bolts went on my mill everything went to hell in a hand basket PDQ