I don't think that we can use the same thing with Bitcoins. Fractional reserve banking might be hard if we are just considering bitcoins, since at the end of the day we have to understand the fact that, bitcoins as a whole are volatile and lending through 3rd parties can cause initial owners to have probelms since they might have to sell instantly because of market fluctuations. How do they decide to do that then ?
Definitely, that's why I said it can only be possible if Bitcoin is valued on itself like by purchasing power or work hours which would make it more stable than when it is purely determined by speculation.
Fractional reserve is definitely not possible in the current structure of the Bitcoin ecosystem and might not actually be possible in the coming years as it's still a very maturing system.
Fractional reserve banking might only work for fiat. With Bitcoins it might be a disaster in making.
It does not even perfectly work with fiat if you consider situations of inflation and hyper devaluation, it's just the current most efficient system.