Sure; a good fabricator could probably cut off the brackets, move them back, and re-weld. But that's not going to help you, because the true footwell IS under the front seats, then you have a shelf, and then the back deck. If you moved it back and the passenger had to put feet on the rear deck and that would be like sitting on the floor.
Why would you want to? You have to ride in the back seat of your own Jeep?
Mine's out now but we will take passengers with us on a few trips and yes I did set in the back to see what it was like. In my opinion a little more leg room would help with the feeling trapped I referred to.
I thought possibly someone else had been there and done that.
Something I never quite understood: USA cars (and Jeeps) are so much bigger than European cars but are so much smaller on the inside. Reminds me of Mary Poppins her magic bag yet in reverse....where does all the space go?
Another thing to consider are your seat belts. I don't know about you, but here in Texas, it's a law that everyone in the vehicle must wear one. Though you could prob rig some lap belts (I think that's legal?), so you won't have to mess with the shoulder belts.