Great idea, but it's not new. In fact, a version of this idea was posted a couple of years ago right here, on the QB. I've been thinking about it ever since. Try searching for it. I will too. I'll be sure to post it when I find it.
This is so timely, because I'm in the process of revamping my space and guess what I have a few of...file cabinets! I have a bank of them in a credenza and desk unit with a couple more. I also have 2 metal ones on wheels that originally came from IKEA and, as I recall, they were cheap. I'm going to make a rectangular ironing board to put on top of them. Then, I can roll them around to close to where I'm sewing, lock the wheels and put the ironing board on top. When I'm done, they can roll back into their place and the board can be stowed away.
~ Cindy