i'd like to make some assumptions in part2 to simplify things. is there such a thing as making an assumption that fits what was given in the problem that makes things too trivial and thus would not be accepted by the graders?
Put yourself into the grader's position. He has to understand your architecture according to your assumptions. Take further into consideration that it is only an assignment - not a real project. Thus your assumptions can be simple but avoid any contradictions !