As mentioned above, STOVL and VTOL require enormous tradeoffs in capacity. The V-22 requires two turboshaft engines with over 6,100HP each to lift its 15,000lb payload. For comparison, the C-27J Spartan, a similarly sized conventional tactical lift aircraft, has two turboshaft engines with 3,400HP, almost double.
So, assuming that scales geometrically, if you wanted something that can deliver the same amount of goods as a C-17 Globemaster, you'll need an aircraft with over 320,000 pounds of thrust. That's basically taking the engines designed for a stretched Airbus A380-900 and putting them on an aircraft 1/3 of the size.
That's not the end of the problem. Once you get an engine that big, you run into two problems 1)cooling the engine, since the engine won't have a large amount of air being rammed into it to cool off. 2)The ground. The ground has two issues, A) the tornado force winds you're going to expose 5 acres of ground to, and B) you're going to have to make sure the tarmac doesn't start to melt under those big hot engines.
Such an aircraft would probably take 20 years and 50 billion dollars to develop and build around 30-100 of the things. They would be incredibly expensive to run, since big engines=big pain at the pump. They would have reliability issues, since they're one-of-a-kind leap in technology. The wouldn't be needed 99% of the time since there just aren't that many things that weigh 75tons and HAVE to be airlifted and it's cheaper to fly conventional aircraft.
In other words, barring some revolutionary anti-gravity technology, such craft are not feasible.
