I don't think that's what the OP means. I think he means is there a way to make a full-size still RAW using the entire multi-aspect sensor rather than just a portion of it as the GH1 does in its 3:2, 4:3, 16:9, or 1:1 modes.
You'd get insane vignetting because the sensor is larger than the image circle of m4/3rds lenses...but with a full frame lens it might do ok...I kind of doubt it's easily doable though, maybe.
Ah, so you're asking for a 14+ megapixel still in 4:3 aspect ratio? That would certainly
seem like something that would perhaps be within the realm of the firmware hackers.
Sorry, I was thinking video-only, but yes dasbin's explanation makes it all much clearer.