System Integration

I was given a task to project manage a workflow document management system. We are using Staffware, CyberDocs and Groupwise as a solution. It has been difficult, mainly the vendors cannot vision the integration of the system, and the user requirements are not capture carefully. Now I have a workforce of two software engineers to start from fresh, and it is difficult for them as they are involved into the project at the latest stage.
One major problems I encountered now is the Users has decidedto opt out from the system.