Guys,
Do not worry that much.
It's just a darn assignment after all. Get something done as fast as possible and move on. Think about it: Sun wants as many certified people as possible. You have passed the difficult part(Step 1). The odds are that Sun will not fail you just for a minor flaw in the design. So any acceptable design should pass the exam. I would not worry about the number of classes, the level of detail, lack of requirements and such.
Given the fact that the evaluators do not have the opportunity to interview candidates, they will be as generous as possible. So my personal opinion is to scratch something down, document it and move on to normal life. As to whether people know or care about the certifications, go to monster.com and search for "Sun Certified Enterprise Architect". You will see if they do.
Take it easy,
Levent Gurses
Consultant