It wouldn't increase the resolution, it would increase the dynamic range; for two shots with different exposure you would do 4 pixels white if both were white, two pixels white if one was full white and the other full black, etc. (your flat panel probably already uses a similar approach to get roughly 8bits of overall color-depth out of 7bit elements)

I meant intensity resolution (or color depth, as you say). Dynamic range is something else - it is the interval [darkest, brightest], or their ratio if you prefer.