well the main purpose in designing one should be for protection, a winch, and off-road lights. best idea would be to check out all the companies that make the hd bumpers and pull ideas from all your favorites, then combine into a bumper that fits your needs. these have always been favorite companies of mine
and if and when you need lights, Hella 500s are the best in my book.
when you make it, use nothing less than an 1/8th inch steel. thats pretty solid, could even run a section of 1/4 inch plate right in the middle for a bit of brute strenght