I think my speculation about coating the absorbing glass has its problems, from other threads and in reading about dichroic filtration it gets less effective the more off-axis you get. So while canon can use a dichroic filter on their sensors Leica cannot, the angle of incidence at the corners means that the dichroic filter would really not work. You would have good filtration at the center and progressively worse filtration at the corners-essentially impossible to correct. coding woudl make no difference.
There were obviously some pipers to pay for the rangefinder design, and having the lens so close to the CCD may have been stellar for film, but not so stellar for digital.
From the examples posted the hot filter on the front seems to fix the problem. Great! now we can move on to moire!
just kidding, I hate that canon mushy pixel look.