I'm afraid you are simply never going to stop aircraft crashing at air shows.
Is true.
A mentor of mine (retired aerobatic/airshow pilot) would preach to we impressionables "No one ever died flying a normal circuit". While not strictly true, I took his point. It's the low altitude extreme maneuvering which is causing the spectacular (not in the favourable sense) crashes. I'm not advocating a ban on low altitude display aerobatics, though I'm not enthusiastic about seeing it flown in larger/vintage or high energy aircraft with very little room for error.
I opine that airshow spectators need to be
trained to understand that "we just don't do that anymore" when it comes to extreme low level aerobatics, and high energy or vintage aircraft pilots planning to cut a margin of error very close. We will not offer to sell you this experience, join us at a show which we are all comfortable presenting with low stress.
and the CAA's oversight role easier...
How much easier do you want it to be?
If the CAA and airshow organizer are not being asked to approve low level aerobatics with very tight margins, it will be easier. Move it all up a few hundred feet, and cancel if low ceiling that day. If the spectators complain, say: "we just don't do that any more". Iphones and binoculars are easily employed to improve the view.
I was at Oshkosh in 1983, when a Siai Marchetti SF260 was fatally crashed right in front of me. The pilot was attempting to impress with a very low altitude spin. The show was stopped, and it spoiled the afternoon for everyone, and it ultimately delayed a lot of our departures for home, with a closed runway.
I recalled this when I organized very small local airshows in 1991 and 1992, when I was easily able to explain my rationale for no low level aerobatics to the two Transport Canada inspectors, from whom I sought the required authorization. Easy show, everyone enjoyed, and low stress for all of us.
Every now and then, society needs a kick start to changed behaviour. If the Shoreham accident report isn't it, I can't think what would be.