For the benefit of the numerically dyslexic, that's 50 oz of broth, 60 oz of tomato juice, 2½ lb onions, 8 cups of rice, and a cup or so of water per steam pan.
Yes, for quantity cookery, you needn't be so particular about the broth. If you've got some extra chicken parts, use chicken broth. Or, boil leftover meats scraps and bones for a beef stock. Or use vegetable stock to appease the vegetarians.
Word from the now wise: Don't try to convert this to rangetop cookery. No matter how desperate you get. If oven space will be at a premium, make a day ahead and reheat. Even if you have to reheat it in batches in the microwave, don't try to make this much rice on the stove. Oy! What a disaster!