I have seen pictures of a 3-pt boom pole modified with a quick attach plate for a bobtach or ATI quick attach for use on a FEL also equipped with the bobtach or ATI systems. If you weld, you could probably make one to fit the JD quick attach system on the FEL. Getting a log dangling at the end of the boom pole, however, would put a lot of leverage on your FEL. You would need a big counterweight on the 3-pt, and may max out the hydraulics on your FEL.
You can also probably buy a grapple to fit the JD quick attach system on the FEL. You would need an additional remote hydraulic setup to operate the grapple.
Finally, a 4-in-1 bucket would grip logs, allowing you to lift them as high as your FEL would lift -- which may not be quite enough for a wall on a barn. You would need the same remote that you would for a grapple.
Good luck on your search. These folks on TBN have a lot of good ideas and experience. I am sure more will chime in /forums/images/graemlins/grin.gif.