Seriously though, please don't do this. It's a very gauche look.
Really, they are just a "nice touch"--if you've got buttons there, they should work, right? Definitely avoid anything that comes new with working buttonholes as you won't be able to easily alter the sleeve length. I do have buttonholes put on most of my jackets just because it drives me crazy to have the non-working buttons, but yeah, they have no practical use.