...the connection between the manual focusing ring and the lens part is electronic rather than mechanical...
Just because a lens has electronic focus doesn't mean that it doesn't have mechanical manual focus. At least on the Canon side of things, focus-by-wire lenses are rare. Most of the focus-by-wire lenses are old, discontinued models like the 50mm f/1.0. The only current focus-by-wire lenses I'm aware of are their STM lenses (mostly low end) and the 85mm f/1.2L II. The rest of their L line is mechanical, including the 50mm f/1.2 L (popular for movie work), the 135 L II, their various zooms, etc.
The big advantage that fully manual lenses have over autofocus lenses when it comes to manual focusing is that most manual lenses have a longer throw. This makes it easier to get a more precise focus when focusing manually. They don't do that on autofocus lenses because it would make focusing slower.
With that said, I think the industry's obsession with manual focus is badly misplaced. When you're dealing with 4K video, you want the focus to be right, not just close, and autofocus is a lot more precise than any human can possibly be, even with static subjects, with the best long-throw lenses, and with a separate person doing nothing but handling the focusing. The only thing holding back autofocus for video use was the slowness of contrast-based autofocus (and its tendency to seek). With the advent of on-die phase-detect autofocus capabilities, that limitation is rapidly disappearing. Add a bit of eye tracking into the mix, and I think you'll find that within the next ten years, nobody in their right minds will still be focusing manually, particularly when they're shooting 4K.
it is often better if the aperture can be set in a step-less fashion
AFAIK, that's fairly rare even in fully mechanical lenses unless they've been modified. Perhaps dedicated cinema lenses are different in that regard. I'm not sure. But even some of my old screw-mount lenses from back in the black-and-white TV days had mechanical stops, so I'm guessing stopless lenses aren't exactly common.
So I can conclude that while having a powered mount is very much desirable on Axiom cameras (and so it will come just a bit later) it is also true that the old lenses are in fact more suitable to the task of shooting movies and so the decision to deliver a fully manual Nikon-F mount first is justified
The problem with old lenses is that they're designed for a world where cameras had relatively poor spatial resolution, and for much less reflective sensor material (film). I enjoy playing with old lenses on a 6D, and they create an interesting artistic feel, but they don't even approach the level of flare resistance, sharpness, etc. that you'd want for a digital 4K cinema camera. So if you're limiting yourself to mostly old lenses, you might as well limit yourself to 720p as well, because you'll be lucky to out-resolve that with most lenses designed more than about a decade or so back.
And if you have the money for modern, full-manual cinema lenses, chances are you aren't in the market for anything less than a highly polished, turnkey camera system.
So I really think that they need to at least lay the groundwork (in hardware) by making the plastic plates in front of the sensor removable and by including USB and DC connectors near the back side of that plate so that the system will be readily extensible in the future. That small change shouldn't require a huge amount of effort, and it will future-proof the design in a way that nothing else will.
Or, if USB isn't feasible, a high-speed serial port capable of at least 230 kbps would probably be good enough.
Just my $0.02.