To make it effective, let's trigger some of your thoughts thru the following scenario and question (assuming kids under 3yrs old):
-when the first child arrived, we tend to put them in the middle-seat of the 2nd row of these mid-size or compact CUV/SUV. When the second kid comes out, we have to place them by the windows (or at least one of them), assuming that this configuration is less safe. Why is the first kid more important, in terms of safety, than the second kid?
I like your line of thinking, here are a few of my thoughts too on infant safety:
The best crash safety device is the driver: DO NOT CRASH! If the driver is alone with a child, the child should go in the passenger side, 2nd row. It allows the parent/driver to reach the child by extending the right arm while still looking at the road. In the center or behind the driver this is not possible.
Besides crashes, infants can choke with toys or blankets, or throw up for no reason so the parent needs to be able to see and reach the kid quickly from the driver's position and still keep control of the vehicle. Putting in the center so it's safer during a crash won't make the kid safer when it gets tangled with blanket and can't breathe, and the driver can't reach the kid until after stopping the car. This is more likely to happen than a crash.
As you properly pointed out: child safety is not only about crashes.
Going with 2 kids:
I tried different configurations based on the age:
a) Rear-facing baby and one forward facing toddler: The rear facing baby goes in the passenger side, 2nd row with proper mirrors so driver can see the baby's face. The other kid goes to the 3rd row, so when a second adult is riding in the car, it rides in the back next to the baby (or 3rd row if using captain chairs, it can still see the baby's face and play with both kids) so the driver can drive without distractions.
b) Both forward-facing toddlers: First configuration I tried was obviously same as case a) (less effort in not moving the seats around), but now there's no need for an adult to ride the 2nd or 3rd row anymore. I also tried both kids in the 2nd row. This is safer in terms of a crash I guess, but kids tend to fight more side-by-side and the driver ends up turning too much attention to the fight and less to the road. Finally, I sent both to the 3rd row as well. They liked it as "something new" but not only it didn't improve safety, it makes it impossible for an adult to reach the kids quickly if there's an issue.
A year ago, I tried a booster with my oldest one. There was one situation where the seatbelt lock mechanism malfunctioned (not in the Subaru, previous vehicle), and the kid was getting squeezed by the seatbelt, the seatbelt had locked (as if something had pulled it really quick, but that didn't happen) and couldn't be pulled out, normally you let it go back a little bit and it releases. For some reason it got stuck and would still be locked, getting tighter and tighter when you let it go back. The kid wasn't strong enough to release the seatbelt yet. I had to go back and release it myself, with the kid freaking out as the seatbelt pressed the chest. Suffice to say, went back to using a child seat for a while longer. That seatbelt only unlocked after I rolled it back completely, and worked normally after that. It malfunctioned one more time, this time without a kid but it got stuck on the seat while folding the 3rd row, going around the back of the seat. It locked when unfolding the seat, and it got to a position where I couldn't move the seat anymore or get the belt from around the seat. I had to force the seatbelt over the corner of the seat after a lot of work (pure brute force), I was getting ready to cut the belt. Once it rolled back completely it unlocked and never failed again.
So yeah, we buckle up our kids so much to protect them in case of a crash, but nothing protected mine from a malfunctioning "safety" device like that belt, and don't even get me started on the Takata issues.