Shouldn't it be possible with a little bit of additional programming in the web app to prevent people from picking a team on their bye week and preventing someone from picking the same team twice (until the playoffs)?
It doesn't seem like too big a job to me.
I guess you'd need a table that stores the all the byes for each week.
The user's past selections are already being tracked so making sure they don't pick the same team twice is just a matter of going through the user's past selections and making sure there is no match.