Also I'm not sure what those cages around the fan blades are suppose to acheive since the cage gap is huge, anything could be sucked in there, needs to be a cage more like a desktop fan.
I presume the cages are sized to keep body parts out.
Unfortunately the laws of physics seriously don't like your suggestion of tighter cages. At low air speeds and with abundant power available you can use tight cages no problem. But when you're at high air velocities to get substantial thrust and where power efficiency is crucial, any obstruction in the air stream is a serious issue. Aerodynamic drag is proportional to velocity squared. When you multiply air speed by ten, the drag caused by each cage wire is multiplied by a hundred. This means thrust loss, as well as draining the batteries trying to compensate for lost thrust. Adding batteries to compensate for the extra power drain increases your weight. Increased weight means you need to compensate with that much more thrust, which in turn means more weight and more power drain. It is a problem that compounds upon itself. You need the cage wires to be as thin and sparse as as you can get away with, short of inviting serious accidental injury.