I prefer physical controls too and love the MF clutch. At least I now know how it works, and it is not as I expected. I was foxed as to why sometimes I got the peaking and sometimes I didn't, but inevitably it was when I was out in some poorly lit room without the time to play.
I have been using C-Af + MF a lot lately with the 300mm +1.4 extender. If a bird is against a busy background and the camera is struggling, I have a chance with the focus peaking of trying to get some in focus.
Edit: I can get focus peaking
and the magnify option, but only when I have actually set it to MF within the camera (which I think is what you know already).... so I guess if you can set a button to switch between manual and auto focus, then maybe it would work with one button press ( providing you have left it set up in the menu).
Edit 2: Actually this is great!! I've finally found a use for the Function Lever, which until now has been surplus to requirements. I've now set it, so that in position 2 it is manual focus. So with a flick of the lever, I can go into peaking and magnify. So thanks
@Stephen L very much for helping me on my journey.... although it might all change when I get the OM1