regarding the digital camera metering rant...
I'm thinking here that the issue might be in the way that RAW images are processed in DSLR cameras.
I use movie cameras for my day job. When we record RAW or (sometimes) LOG images, the recorded data remains the same always, but the ISO setting is saved to meta data for RAW processing later. (in LOG mode, changing the ISO, and thus exposure, moves the image up and down the scale).
What that means in practice is that shooting a low ISO image essentially exposes to the right, and a high ISO exposes to the left, if you will. But the live monitor image is adjusted to show the metered (intended effect) exposure. It also means that highlight DR is reduced at low ISO and shadow DR is increased. The opposite is true at high ISO settings.
If this were the approach taken in a DSLR still camera, metering can be left as it is, allowing for fully adjusted JPEG and live view (or review). Changing the ISO setting would be how one would ETTR, knowing that there will be less highlight protection the lower the ISO setting, but maximum image quality (providing you don't clip wanted highlights!)
If the camera had the feature of showing clipping in the viewfinder for each color, it would be easy to maximize quality by changing the ISO setting only. No special ETTR metering required. For example, the RED cameras have a "traffic light" in the view finder showing RGB. When the "R" light goes on, you know you're clipping the red channel and so forth.
As it is now, from what I can see using my Canon 5D, is that analog gain is applied to the sensor data as the ISO is increased, before recording the RAW image. Maybe there is some noise processing advantage to this, I don't know. This is what makes it necessary to think about exposing to the right. But Arriflex and Red certainly don't do this