All good points
I'm not convinced that 500' would be the highest it could be built. There are skyscrapers being built that are upwards of 1500-2000 ft tall, and they are heavy, built with concrete for extreme compression loads. Guy wires are made of steel, working in tension they are extraordinarily strong. I think a 2000 ft tall funnel inlet would be feasible. Whether anyone would want to build one is another story. It would be pure laziness if someone didn't try it at least once, it's so simple.