Mart,
Sorry Dave, but this ain't gonna happen.
Never say never.
Seriously, thanks for submitting valid concerns. In response, and to pursue the pros and cons;
IMHO there are two basic concerns;
~ 1/ Improving the power to weight ratio of electric drives.
~ 2/ Optimizing the lift to weight ratio of the rotorcraft.
1/ The first concern is outside the domain of aeronautics. However, we know that significant improvements will be coming.
2/ The second concern is the domain of the rotary aerodynamists.
~ We know that inexpensive electric RC craft are being built today.
~ Is there any reason why an inexpensive full size homebuilt, with a long tether to a ground-based genset, cannot be built today?
~ Is there any reason why an inexpensive full size homebuilt craft, with a VERY short flight time, cannot be build today?
Consider that the flight time of all three can be improved, today, by adding the aerodynamic advantages of two independent rotors and single-bladed rotors.
A response to your concerns about the single-blade rotor;
The bending moment input from the single blade will put mass way up.
Why? Look at the successful Bolkow rigid blades near the bottom of ;
this web page
You can't make it teetering 'cos there is no lift symmetry.
There is symmetry, however it is between lift and centrifugal force. See the 4th drawing in the middle of ;
this web page
if the 1P lift doesn't shake it to bits first.
It appears that no one had tackled this serious problem, until recently See ;
this web page
It will be done. And, what a cheap and fun project.
Keep the concerns coming.
Dave