I am confused about the OP's remarks about dome in and dome out. Lets take an example where a landscape is being taken where one cannot get to the subject. Example shooting across the Grand Canyon or at Sentinel Bridge in Yosemite photographing Half Dome with snow.
For reflective meters, I take light readings minimizing the sky, that is I aim the meter down somewhat. When I took a photograph at Sentinel Bridge in Yosemite photographing Half Dome with snow, I used a average meter reading without the sky using the Hasselblad PME prism. Then I used my Nikon F100 with a zoom lens in spot meter mode to read the snow on Half Dome and the darkest shadows in the tree area at the river. Using the three reading, I averaged the two spot meter readings and compared it to the average reading resulting in capturing and SBR range of twelve stops. With a lot of burning and dodging I got a superb print on paper with a range of six or seven stops at best.
For incident meters: Dome in the meter is where would be standing and aiming away from the subject. Dome out, aimed the same way would be an average reflective reading pointing directly away from the subject. The dome in reading measures the incoming light to the subject; the dome out reading is the light reflected by the anti-subject. If I am understanding the OP, I fail to see the use of the dome out reading. Please correct anything I have said where my understanding differs from the OP and then explain how the dome out measurement would be useful in this example or any additional example.