There was a joke, in lighter vein.
Some one advertised that his Stabilizer has a spec with input 0V to 260V AC 50Hz, and output 230V 50Hz, and load of "X" amps.
The person purchasing came and asked them. "It is Fine, show me with "0V" input and 230 V output and i want many units."
Please do understand that what you want is reasonable wattage from the unit even with all the stabilization-( i fear, as the speed varies, voltage changes, so becoming input "anything from 0" and output say 20 V. ).
As the input reduces ( to a limited point and not like "0"), the output would come but can't deliver the load.
In such a design perhaps, you need a standby support of a battery also.
I would suggest that your concept should be logical as Energy can neither be created nor destroyed.