Assuming there is nothing wrong with the drywall itself, I would guess that it would be less expensive to hire someone to come in and re-tape and re-texture than it would be to install steel everywhere.
That being said, I do like the corrugated wainscoting with white upper idea. I would say skip the color band though, that sounds like a lot of work and it would probably make it look very busy in that space.
Here is another option to consider... do the lower part (3-4') of the wall in the accent color you like, and do the upper in white - that way all the steel would have the same pattern throughout... just a thought.
