it depends ... if the legs extend into the body of the chair as support for the corners, it's hard.

Finding tall legs will be a problem

You have to saw them off then figure out how to add legs you like.

Ditto. My money's on that the legs are extensions of the frame and not just bolted on to a sub base on the chair.

If you are going to add legs alone, pretty tough to do. If you are going to add a whole sub-frame with an H-stretcher and legs, a bit easier, depending upon how fancy you want to get with the leg geometry (straight vs. tapered vs. turned)

If you really hate the legs you could reupholster with a tailored skirt