IMO, the NEX seems like the best the choice for mounting manual focus lenses with its peaking feature. I haven't tried peaking yet, but it seems to be a more accurate and quicker way to manually focus lenses than using a magnify feature on either the Pany G or Oly Pen, unless the magnify feature is an auto-magnify feature (magnifies at the turn of the focus ring), which will not happen with lenses without electronic couplings.
Peaking might actually be better than using a rangefinder patch! Yes, quite sacreligious, particularly coming from the mouth (or keyboard) of a Leica user! But I suppose I better not spew such venom from my mouth just yet, given that I haven't tried peaking yet!
Now if slightly switch thought here and think of "complimentary" cameras, the 2x crop factor actually works in my favor. Why? Because I can take the same exact 90mm Leica lens and treat it as a longer telephoto with an equiv FOV of 180mm. See? 1 lens two uses. The M43 cameras also provide telephotos beyond what is feasible with a rangefinder, Autofocus when I want it, AND Macro. All things a rangefinder may not be the best tool for the job.... and with a compact size (body + lens) that doesn't weigh too much more than the M-system by itself.