It appears that a lot of Jeep owners who use the CB for club-type outings are happy with various rear-mount antennas despite the limitations. Since the only thing many of them want is to be able to talk to the group which is within a mile or fraction of each other, what's to worry about? And it looks so cool whipping around back there!
But hanging an antenna off the back on a spare tire mount or whatever leaves the antenna just hanging there without the needed sheet metal required for best results. It usually takes some mesh copper straps to cobble things together well enough to get by, but it's still a compromise.
Since there's no sheet-metal roof or even a trunk on the Wranglers, the next natural, horizontal sheet-metal place is the hood. I know the OP doesn't want the antenna there, but that's the place. Fender mounts get close to it, but the on-hood mount is the best solution, performance wise.
Aesthetics are nice, but they don't haul the freight.
For me, I plant a mag-mount Wilson 500 or 1000 on the hood of my TJ whenever I need radio communications in the field. It's not a pretty place to have it, but it's a tool, like my HiLift jack and the winch and the rear-facing work light. And practicality beats aesthetics every time in the field.
So for me, the hood mount works about as well as the missing metal roof would, and surprisingly so, because I was anticipating lots of RF gremlins popping up from the engine ignition, alternator and/or other potential underhood threats. None showed up when I put the antenna there, so count my blessings, the thing actually works.
Beauty is in the ears of the receiver.