Originally posted by Sinister I think you got me wrong. I am aware of the fact, that the "air" in the module itself is a non-changable constant. What I am asking for is a flat body, without the battery bulge - like an MX - which easily slips in my bag. Next to it the adapter and my FA43 or DA21 and I'd be happy. And the easiest way to achieve this, is the GXR.
Maybe, I got you wrong. I actually have the same dream, owning an MX myself.
But I had to learn that the extra bulge in an, e.g., K-5 over an MX is crowded with electronics, incl. a sensor, AA filter, SR mechanism, LCD screen and PCB boards. All of this would not go away if removing the battery grip bulge, i.e., overall depth of a K mount camera would still remain the same, a K module GXR or K adapter NEX included.
However, I see your point of removable bulge for transport reasons. If you have enough pockets to stuff the rest. I am just not sure that this is enough justification for a K mount mirrorless. If this is this important, you could design a foldable mirror box which folds tight with the mirror locked up in power off state. The fact that nobody ever tried it tells me it isn't this important.