Hell, it doesn't seem like that many years ago that you would see trucks with bumpers made out of railroad rails or 4-6" diameter pipe... Considering the fact that railroad rails can weigh up to 155 lbs per yd, that made for a bit heavy bumper....
formatting link
I even remember seeing one made out of a railroad tie at one time...
You are definitely going the other way in your design... Have you considered possibly just replacing the stock bumper with something more sturdy? Even if I wasn't towing anything, I would want to replace the factory bumper... Bumpers should be able to withstand backing into something at a slow speed without any damage to them... Perhaps make yourself a bumper out of 4" steel I-beam? Here's the weights and dimensions for various sizes...
formatting link
All you would need to do is create a couple of brackets to mate with the existing factory attachment points... You could either weld a receiver hitch adapter underneath the I-beam or just drill a few holes and mount a plate similar to what you current have, but without the bend... I would put the I-beam in an orientation so that it looked like an 'I' instead of a 'H'... The mounting brackets would be welded to the inside channel of the I-beam and as such, supported on 3 sides, making the weld fairly sturdy...
formatting link
This would still be a fairly cheap solution... Not owning a TJ, I'm not familiar with the attachment points for its bumper... It is my professional opinion that one should design for at least as great as the weakest link in the existing system... Basically, there's no need to put a bank vault door on a room that has sheetrock walls...