Is it true that 5dmk3 doesn't have that moire/aliasing issues 5dmk2 has?
The 5D3 may be slightly better but both cameras are going to suffer badly with aliasing, and no filter will really help without decimating the resolution. You're only recording from about 1 in 9 of the pixels on the chip. Thus almost 90% of the image is falling down the holes in between, and worse still the R,G and B source pixels being used for each output pixel will be some considerable distance apart.
So details will drop in and out of existence as they move across the sensor. Monochromatic edges will have serious colour fringing and bright details will cycle through the rainbow as they move. All very familiar to anyone who's used scientific high speed cameras with no low pass filter. That said, if you deal with this in post on a shot by shot basis, then you must be able to do a better job than Canon do in camera. ACRs colour noise reduction handles the colour artefacts remarkably well and I believe the moire reduction is pretty impressive for stills.
But this is all throwing some light on why DSLR video generally looks so terrible. Canon have really done a pretty amazing job getting rid of most of the colour fringing and detail flickering, in camera, in real time. Just wish they gave us the choice to turn that 'feature' off!
