No idea as to the height you will need. But because of a spinal cord injury, I am the proud owner of 2 walkers and a power chair, I cannot stand without some sort of assistance. My lathe is set up to use a bar stool, where I am half sitting and halfway standing, but still supported by the bar stool. In my shop, I have almost every tool set up at a level so that I can use the bar stool. I had to use the bar stool, so that I could keep circulation to my legs, a chair was hurting my circulation.
What I did, was set each tool at a height that I thought was "good". First I used 2 saw horse kits, and kept changing the leg height until I felt comfortable with that tool. The sawhorse brackets, were the $4 tin version from Harbor Freight. I wasted a couple of 2x4s on getting the heights close to what I wanted. But in the end, I can spend hours half sitting on that stool and be pretty comfortable.
I have looked the Gunmaker's Horse, by the way I do like your choice of "title" for it. At one time I had a similar setup for a lathe stand. If I was to built one, I would have to build a bench top version, so that it could be clamped or bolted to the workbench. There is no room in my shop for a floor version.