Alfatcop --
Since Microsoft released Project Server 2007 and introduced the Proposal new
feature, we have recommended to our clients and our students the following
Best Practice for using Proposals:
1. Create only a high-level proposal with no tasks, or with only high-level
tasks representing the Phases of the project. DO NOT attempt to build a
detailed project, as the effort is a waste since you can only assign one
resource to each task.
2. Do not assign a resource to any task. Instead, create a Resource Plan
associated with the Proposal to "reserve" the resources in the future.
Remember to publish the Resource Plan so the other PMs can see the resources
as "reserved" during the appropriate time periods in the future.
3. When the Proposal is approved and the PM converts it to an enterprise
project, he/she must remember to convert the Resource Plan to use the
assignment information in the actual project and not in the Resource Plan.
Just a couple of thoughts about how to use this promising but disappointing
feature.

Hope this helps.