Everybody is too focused on the project,the wrong question is being asked here.It should be "How do I PROTECT myself as a developer in a project that is heading for failure." All throwing together weekend solutions will do is waste your private time and put a big target sign on your head,its only worth doing that if you have a fair chance of solving it and you will get the lions share of the credit if you pull it off. Look for other roles internally or externally, protect yourself how you can and emotionally distance yourself from it. Worry about your career not the stupid project.