Okay, based on my research, the airbags are not the problem. Roadtrek even today does not have SRS for other than the front two seats. I wrote them to check this.
The greatest problem with the RVS is the potential for the back part to come aloose and become projectiles. Roadtrek said that its testing exceeded govt. standards but again one can see that if there are few govt. standards, this is a risk. And there seem to be no real standards on the projectiles.
Another issue for Class B safety is that of fire. Gasoline and propane are highly flammable and leaks can catch on fire. What about the surfaces inside the vehicle? It seems that it is much safer to have an rv with no gas or propane at all. The all-diesel would be the best.
Further, MB Sprinters are likely safer than the cutaway vehicles because MB Sprinters are only allowed specific modifications.
Consequently, it's most likely that the safest thing is an all-diesel Sprinter base. I still don't know how to compare the older and the newer ones, but the fact of your having brought up this point helped me look at the RV purchase from a safety standpoint. Thank you.