I have seen this video already a while ago but now, Infinity Hobby has it in their product news. Apparently, some company is making propeller hubs to use heli blades with multirotors.
That allows using of ridiculously big propellers, leading to very efficient setups. Additionally, heli blades are dirt cheap, compared to multirotor blades and with the adjustable pitch (!), there's even no searching for pusher-props any more.
Can't wait until this is actually available!