Record multiple frames from single exposure?

[T.Hunziker]

Would it be possible to have 2 (or more) files, each with different ISO settings, saved from one physical shutter release?

I've been thinking about alternatives to bulb-ramping for time-lapse that don't rely on a meter or trying to predict the entire exposure change ahead of time.
Let me describe the workflow of what I'm thinking about:

Example: The typical day to night time-lapse. 
I start shooting at a metered exposure of f/5.6 (stop will be constant throughout) 1/125th sec. with an ISO of 100.  While I'm shooting, the camera is simultaneously recording a 2nd set if images with an ISO 200 applied.  1 stop brighter.
When my meter begins to read minus 1 stop, I change the shutter to 1/60th sec. and so on, 30th, 15th etc.

Bear with me, hopefully it will start making sense in post.

So now back at the Mac, I create 2 synced video tracks, each with a one stop exposure difference.  I can then simply do a long cross fade between the tracks to create the ramping.  This would of course be repeated for every full stop of exposure change (the1 stop increment is for example purposes and could be more or less than 1 stop).

Of course this method would mean more exposures and more processing time, but flicker could be completely eliminated.

I thought of doing this using AEB but figured that the gaps between frames would get too big on the longer exposures.

[1%]

makes sense but probably not possible. the iso's are a physical thing. the sensor is only read at 1 ISO at a time.

[T.Hunziker]

Shucks!  I guess I'm back to 2 bodies, 1 lens and a beam splitter.

[Francis]

Looks like it. Please don't post the same topic on 2 boards.