My whole reason to make bread is to try to avoid the extra unnecessary ingredients in these kinds of mixes.You probably seen for sale Bisquick, its a form of self rising flour, just compare the ingredients. Anyway, a box of that on hand with some buttermilk and couple eggs makes good pancakes, or biscuits.
As for adding cheese, or cheese and chopped spring onions or peppers, for a quick job I would simply add a handful of chopped/grated bits to the batter of the two ingredient bread previous, just like @Meadowlark did with the jalapenos.
For yeasty bread, do the same - just throw it in. Sprinkle a little grated cheese on the top with some sesame seeds.
As previously said, experiment and have some fun.