I hear what you're saying about the gas but when the RR Diesel (according to LR) get 24 mpg combined you start to ponder. I wish I could get the G 300 CDI Diesel...no, not in the US? Starting to sounds like the Defender world...
I watched a driving review where they got 30 on the hwy no problem. My guess is that if you "try", it will do quite well. Remember, it's a lot lighter now too which will help with in town mpg.
I love the G, but if it's purely about safety inside regarding airbags, I don't think there's really any comparison between any of the current RR, LR4, Toyota Land Cruiser, LX 570 vs a new G because the G still does not have side torso airbags in the 2nd row or any front knee airbags. The G has 6 air bags (front dash both sides, curtain covering 1st and 2nd row windows, and front side torso. It's also a bit snug for 3 people across the 2nd row where the others I listed all have more width for 3 people. The Land Cruiser/LX has so-so 3rd row space with the LR4 having 3rd row for even tall adults.
The LC/LX, LR4 all have side curtain into the 3rd row area. The LC/LX both have 2nd row side torso for a total of 10.
If I were looking to get something for hauling kids/people, it would be the LR4 unless never more than 4 people. For overall safety including body structure design in rollover or any type of civilian world impacts, it would be either the modern designs. The Mercedes GL has a huge amount of space for all 3 rows but I didn't list it because I don't consider it up to par on the off road capability assuming that mattered for you
I like to remind people, including myself, that a large factor in the "safety" equation is also avoidance and my experience in solid axle vehicles vs the ones I listed, the modern vehicles are much quicker to maneuver in an emergency.