[PbFut]

As long as the line you are considering does not bulge under pressure there is no particular reason it would not work. A brake line can see pressures as high as 8-1200lbs at peek.
Hard line installed correctly will have a longer life and generally be safer from failure. I would probably not use flex unless no other option. Making hardlines (Bends and Flairs) is not hard with the correct tools and is kind of satisfying when completed. You have flex at each wheel, so it's not much different, but notice it's only used where movement is expected.