Back to Romain's crash, I think the barrier separation is the root cause of the problem and something that would be worth addressing for next year. There are at least four problems if the barrier allows the car to penetrate it:
1) People may stand behind barrier thinking they're safe there, but the car could come through
2) The car penetrating the barrier may injure the driver unpredictably as it goes through (albeit the Halo helped on this occasion)
3) The driver may be trapped in the car if it's enveloped in the barrier (a problem in case of fire, or if the driver needs urgent medical help)
4) A car enveloped in the barrier can then be subject to pulling and twisting forces, not just the 'pushing' forces its designed to handle (hence breaking apart in an unexpected manner here)
All of these can be avoided if the surface of the barrier can remain intact - it's ok if there's some 'give' as it deflects, but it shouldn't open up like this. The Halo wouldn't have been needed if the car hadn't penetrated the barrier. Also, I think it was the twisting force caused by the front of the car being wedged in the barrier that opened up the fuel lines, causing the fire. And even with the fire, it wouldn't be so bad if it had been easier for Romain to get out.
There are quite a few examples of tragic accidents where cars have got tangled up with barriers in the past - Jochen Rindt at Monza and Francois Cevert at Watkins Glen. I'm not sure what the answer is, but I think that's the question.