The one thing I can think of, that might be an "easy" helper, is the foam used in NASCAR (and WRC I think). Of course, that foam might've gone off in the first hit, but it would've taken energy as well.
I'm not a huge fan of the Tech-Pro Barrier (I know it wasn't there in this case though). I think on all very high speed corners like this they need something like the SAFER barrier. It does a much better job of distributing the impact energy compared to a tyre wall (you also tend to "dig in" with a tyre wall). You would still get injured of course but at those speeds something more advanced could have saved him. I've seen drivers walk away from huge accidents with SAFER barriers and that's proof enough for me. I know other cars were involved but sometimes as a circuit you must do everything you can to minimise risk, especially at corners like at Eau Rouge.
Some years ago there was a slightly similar incident in the Spa 24, where in heavy fog a car went off at the exit of Eau Rouge head on into the tyres and spun like a top across the track. Thankfully no-one collected him but he was in a very serious condition for about a two months with bad head injuries and broken bones. The hospital put him into a coma to minimise the brain swelling. There was literally nothing left of the car but the main tub, such was the violence of the impact.
Maybe they should have upgraded the barriers then. It was an amateur driver but even so, track safety is one of those things that needs constant work on it my view.
However as others have mentioned the mandated crash test for Formula 2 cars I think is a one impact type test? Whereas F1 nowadays has some tests whereby the crash structure is hit more than once to make sure it can take the punishment of being hit by another car after a side impact for example.
Once his car took the first (very) heavy impact the crash structure was badly compromised.
Such sad news, Anthoine Hubert's family must be devastated and I know they won't see this but my thoughts are with them at such a difficult time.
My thoughts are also with Juan Manuel Correa because he's still in a very serious condition and judging by the reports of his injuries he's got a long journey of recovery ahead of him.