Creating a BW workspace using a composite provider

[#1]

I want to create a BW workspace using a composite provider that joins two ADSOs, but I encountered an issue.  I am working in BW4 and want to use a composite provider as my main provider in the workspace settings of RSWSP. The composite provider is a join of two ADSOs.  I have tried multiple ways to get around this.  First was to create a Union node in the composite directly above a Join and assign it to the main provider of RSWSP.  Only then can you see it in the Central Providers section.  Second was to do a Joule suggested, and that was to drag in the Composite provider in the Central Providers section along with the two ADSOs, but the composite provider is not available unless it is in the Settings for main provider section first.  Even there, you cannot add additional ADSOs once the Settings for main provider has been established.  Please see attached.

I should not have to create a new model.  The Composite model already exists.  I am just trying to use what is already built, not reconstruct what is already built.  We need this tool so we can allow our Power Users to use the Workspace Designer Query functionality.  We would assign this capability as a self-service capability for power users, that could help generate queries for our infoconsumber base.  Giving them access to Eclipse is not the ideal state. 

Steps;

Original Scenario cannot be used as a main provider on the Setting Tab of RSWSP

Workaround #1, tried to put a Union as the top of the new Scenario.

Workspace designer does allow it in the Settings for main provider:

However, when looking at this in central providers, it remains in Error:

Attempting work around #2, tried to add ADSOs after establishing Settings for main provider.

Please also note that there is no “Composite” provider to select from in the Central Providers area.