I’m kinda warming up to the thought of a rotary shutter... Of course the Pen F had interchangeable lenses, some rather long, too. The Pen frame-size was very similar to APS-C. And it was produced way back in the mid-1960s. The shutter could be made of carbon fiber or titanium foil to keep the inertial low and the speeds higher than the Pen’s 1/500.Rotary shutters can't have a very high max speed, unless I'm mistaken. My Robots can only do 1/500. The size of the shutter opening also has be pretty small to keep the rotating disc's inertia low (and thus max speed high) which rules out using the design for longer tele lenses. For this reason I would think that its unlikely that Fuji would be investing a lot into using a rotary sensor as the design could not be used for an interchangeable version of the kit (or at least not with one that could support both high top speed AND use with longer tele lenses).
Also of note, the compact X100 body needs room for the rechargeable battery as well...