Here is a question for the signal processing experts. One method used to avoid aliasing in CT scanning is to jiggle the sensor slightly, smearing the signal over a few adjacent photo-sites. There seem to be some related patents for photographic applications at HP and Canon.
My naive idea: use the ultra-sonic vibration system of the sensor dust removal system, at lower amplitude: could suitable jiggling of the sensor produce a useful low-pass filtering effect? Especially given Guillermo's observation that photo-sites with high fill factor are already quite good at filtering spatial frequencies that are far enough above Nyquist, so this might only need to have a narrow "absorption band."
The appeal of course is that this could be turned on and off according to the situation: just flip the E/non-E switch.