Were you thinking of a single portfolio that would update every week, or of having the ability to add/create a new portfolio each week? I think I could see a preference going either way. On the one hand, it might be nice to be able to have a constantly updating portfolio, that just shows the current roster each week. On the other side, I could see where you might get attached to several stocks from a given week, and want to keep track of those.
I'm not a programmer, so I can't speak to the difficulty of building one over the other, but would be interested to discuss which you might prefer, so I can have a good idea of what to suggest to our development folks.