When Portal is installed it is assigned a unique ID. This ID is in the wpconfig.properties. This ID is stored in the Portal database and this could cause a problem. But more importantly, all the Portal applications are assigned a unique OID when they are installed/deployed and these OIDs are used to map the app code to the customizations and other data in the database. Upon a reinstall you will not be able to guarantee that the Portal will assign the same OID to these apps so then your configuration will be corrupt....ie, the OIDs assigned in the WSAS config will not match the OIDs that exist in the database from the previous install.

You could accomplish what you are trying to do if you had a full xmlaccess export of your previous environment. Then once your new Portal was installed and pointing to CloudScape you could then perform a full xmlaccess import and then edit the wpconfig files to point to your existing database and then run the connect-database task to reconfigure the WSAS datasources to the existing database. Running the xmlaccess import would ensure the OIDs would be the same because it comes from an export from the previous environment.