Theoretically, could an aircraft, using any manner of self generated air flow over the (fixed) wing, ever gain enough lift in order to take off (or just simply lift off the ground) at zero forward velocity?
I am guessing that if an aircraft and its engines were light enough, you might be able to provide a high enough airflow across the wings using the propellers (akin to forward motion) - although obviously I am fully aware that most of the important control surfaces would not be functional. This is just theoretical.
To what end.. well... a more efficient understanding of self-generated lift (possibly?) might result from research into extreme blown flap/wing super-STOL utilization. High-lift, small transport aircraft operating out of small congested city air/heliports with very small runways.
I am aware of the limitations of such designs, such as inefficiency at higher speeds and, in the absence of variable form and geometry (which would add too much weight) the fuel usage would become prohibitive. It's purely an idea for speculation.