My next project is a rear bumper for the Vitara.
I have a vague idea what I want, probley include a tow bar into it with out making it to heavy.
Towbar on a rear bumper? Maybe on a front bumper. Hitch on the rear.
The biggest problem with building a bumper is figuring out the attachment points. Once that is done, it's a matter of fabbing some brackets and then welding bumper onto them. Even better, take mesaurements from the brackets, remove them, then weld the bumper onto the brackets.
As reb says, the simplest design is a big, 'ol nasty boxbeam. You could get fancy and fab a bumper that fits the space of the OEM bumper, but you may end up with something that is heavier than it is pretty.
As for the towbar, I originally bought a towbar from Walmart. It had U-shaped pieces that attached to the bumper or frame. The towbar attached and pivoted on the u-shaped pieces. I built a box-beam bumper for my Samurai and welded these u-shaped pieces directly to the front of the boxbeam bumper. Since then, I have flat towed my Samurai over 2200 miles without a problem. And I simply removed the towbar from the bumper when I went wheeling.
Hope this helps!