As far as POINT 1, this has been very heavily studied in the cycling world.

Among the durations I have data for, world class cyclists can achieve 10-11 watts/kg of body mass for 1 min and around 7 watts/kg for 5 minutes. Those data yield different power outputs for cyclists of differing weights of course, but watts/kg is actually what's important here.

I don't suppose they'll have a professional cyclist on hand to pedal, but for reference, I'm an amateur cyclist (with a powermeter on my bike), and I can sustain ~500 watts for 1 min without killing myself too badly. That's about 7.5 watts/kg for me.

Regarding previous posts, the most efficient design is of course going to be a single person, since the problem is completely limited to power vs. mass. Also, simple leg cranks may not be a bad idea (as opposed to additional appendage/torso/etc. cranks), since in a duration this short, you are pretty much limited by V02Max/Anaerobic threshold, and I don't think adding arm cranks would fix that.

I'm sure they went with such long blades for lift to drag efficiency, but of course that changes if they contort. My personal belief is that there is going to be just way too much drag/friction to lift an object of maybe 75-100 kg with, say, 500-1000 watts.