Had a chance tonight to play around with the F/22 Bracketing idea and came across the first problem: sensor dust etc.
That is, at F/22, of course, any dust on the sensor will be pretty clear.
Here is tonight's test image: this time taken with my Irix 11mm at F/22.
I took seven manual images between about 0.7m and 1m.
The sensor dust is clear on the wall.
Bottom line: this could be the end of the F/22 Bracketing idea :-(