I suppose you could, yes. If you wanted to make all this happen algorithmically you'd end up with a super-sized key that was a concatenation of all the keys you generated for each of the sub-algorithms, where the sub-algorithms would each consume their respective key chunks.
You don't have to concatenate your keys, simply XORing the random bitstreams together works fine (my intuition says that XORing them would provide a stronger result).
