Yeah, p2p is similar to p2p lending, which is not exactly a mutual credit union. The difference is the social factor which means they'll help each other, but also that they'll trust each other.

Material insurance (where you're insuring a certain $ amount) works because people have utility curves that justify it: the utility of losing 1M is much higher than 10 the utility of losing 100k.

So for p2p, 10 people can buy just 5 insurance contracts and distribute the rest of the risk amongst themselves.