This isn't really my area, so I'm probably wrong... I'd always assumed that RAW files were, well, raw data straight off the sensor (or as close as possible)? In which case, you could standardize the container format, but I wouldn't think it was possible to have a standard format for the actual image data. Would appreciate if anyone could correct me (a quick skim of wikipedia didn't clear it up)
Most image sensors are quite similar (ignoring weirdos like X-Trans and Foveon) so they could use the same format and decoding algorithm. It's a 16-bit integer (padded out from 12 or 14 bits) for each pixel with a Bayer color filter. Maybe throw in some parameters like a suggested gamma curve.
Foveon has awful Foss support so far. Older foveon models also require an older version of windows to run the antiquited software to process raw pics, it's maddening.
The algorithms for getting a useable image from a Foveon sensor are very non trivial from what I understand - the different layers don’t separate light perfectly into red, green, and blue bands, so there is some fancy cross layer processing you need to do.