Venture Capitalists are already like reverse insurance companies. They cover lots of people in the hopes that one of them will hit a rare event and it'll pay for the others.
Buying shares of a single startup is sort of the equivalent of betting on a specific horse to win a race. But what's the equivalent of lay betting (betting that a specific horse will NOT win)? Shorting? But you can't short a private company.
But wait, venture capitalists are already betting that their startups will make money. What if they were willing to double down a bit and accept lay bets? Say there was a kind of specialized short agreement that let you say "here is $x, if in N years company Y has less than $z profit/revenue, I get K*$x. Otherwise, VC gets to keep my $x." You could sell it to VCs as a way to do options trading on their own startup investments, plus it'd be a good way to get the wisdom of the crowds or whatever.