As the title says, I think this feature during or after rendering would be cool like multilight or simulens (not talking about the new realtime render feature that is coming in the future), imagine changing some lights power in multilight and enabling autoexposure all you scene adjust to the new values to avoid any over expose or under expose areas.
The best example that I can show you is from this little software http://www.daionet.gr.jp/~masa/rthdribl/
In this software if you rotate the view and look directly to a light source you can see how the camera adjust the exposure and the same happens if you look to an area without any light source.
PS. Sorry if I'm being a little ignorant in this topic or I don't explain myself in the right way