Magneto didn't walk across multiple metal platforms. He stepped on one and floated across on it, using the other two as weapons. I get what you're saying, however, but though the idea seems interesting at first, I don't think it would work out. I've had my flight glitch a couple of times to where my character would run on air rather than actually fly. At the max speeds, it looked really bad. Earth Flight already stands out from other powers. It changes depending on he ground you stand on. Example: Use it on ice and you fly on a giant chunk of ice. Use it on the street and you fly on a chunk of concrete with metal bars sticking out. If you use it in the sky, you ride on a storm cloud. No other power gives you that. It definitely sticks out from Ice Slide, since EF lets you stay in the air and is much easier to control.

As for Wall crawling... While everyone would love that to happen, it never will. It has been mentioned hundreds of times in hundreds of different threads, all with the same answer. It could only be possible if they remapped every single surface in every section of the entire game, which is a crap ton of work for very little reward in their eyes.