Security :: Schema Consolidation And User Schema Mapping Based On Service

We have an application with many separate databases (one per customer). Given they share the same business requirements (service hours, change mgmt etc), we're interested in potentially consolidating the separate DBs (which are relatively small) into separate schemas within a fewer no of databases to reduce the overhead.

Our issue is that the application is hard-coded to use a specific administrator and application connection user name. Changing this is unfortunately not an option.

Given this limitation, is there any possibility to map a generic user into a customer-specific schema based on the database service that they connect to? Each customer connects to different database services but may use the same user name. We considered using private synonyms but this seems to acheive the opposite (i.e. many different users could connect and map to a single users schema). One thing to point out is that where there is a single user name, it is acceptable for a single password to be used across the different customer DBs as they will be a single admin/user.