I agree with the opinion that merging changes with in same model by different users will be a Mission Impossible thing. I will have to see if i can manipulate the xml definitions with in the model and able to merge changes based on those definitions.
I have been recommended the Crossvista TEAM product before too by another Collegue (They have successfully implemented it in Canada for a client) and heard lot of good things about it. With the time frame and the budget currently allocated to this project, i think it will be next to impossible for me to convince the top dogs to get CV TEAM.
Maybe we could consider the product on day2, after seeing all the issues with the BPM deployments using Deployer :).
Thanks for your inputs Rob, Senthil. I will test the model that i have discussed earlier with some additional functionality for merge and let you all know the findings. Appreciate the help!