Did you try INCLUDES(TEXT(StageName)..

You should use TEXT(StageName) to retrieve string value out of the Picklist.

Try this:

INCLUDES( TEXT(StageName), "Final Proposal", 
OR( ISBLANK( Geography__c ), ISBLANK( Languages__c ), 
ISBLANK( Customer_Base__c ), ISBLANK( Number_of_Agents__c ), 
ISBLANK( Additional_Resources_Required__c ), 
ISBLANK( Program_Length_In_Months__c ), 
ISPICKVAL( CRM_List_Requirements__c , 'N3 Provides'), 
ISPICKVAL( CRM_List_Requirements__c , 'Client Provided '), 
ISPICKVAL( Proposed_Commitments__c, 'KPI' ), 
ISPICKVAL( Proposed_Commitments__c, 'Metrics' ), 
ISPICKVAL( Proposed_Commitments__c, 'Results' ), 
ISBLANK( Non_Standard_Program__c ) ))

Ref:

https://success.salesforce.com/ideaView?id=08730000000Bq9SAAS