research on schema design

Hi all,
I currently in a process of redesign our schema structures , and I'm looking for optimal way of doing it.  

Here is what I've in mind:  

The schema structure should be as optimal as possible for the following considerations (Starting with the most important):

• Maintainable - developing , installing and patches should be simple and with minimum interface to the system.
• Backup & Recovery - Backup and restore the schema should be easy.
• Cloning schemas - Building a new environment (production, Q/A , integeration) should be quick and simple.
• Secure - Maximum security between users & developers.
• Modularity - Support in adding new modules

I come up with the divisions of schemas:  

• CoreSYS - contains common utilities which are used with all the applications. For example - Logger utility , formatting routines This schema hold code (pl\sql , java , oracle types) ,and configurations. This schema has a lot of privileges (almost DBA). No one should login directly to this schema.
• CoreSYSTEM - synonyms and views on coreSYS objects. This schema has a minimal privileges and several execute privileges on CoreSYS objects . It's primarily use by field engineering personal.
• SHARED - contains input tables (data from external sources like files) ,which all the applications use.
• <App>SYS - contains application configuration and management tables. This schema is used by all the application modules ,
• <App>SYSTEM - contains the all the data which is generate by the applications modules. This schema is used by all the application modules.
• <App>User - This is the point of login for the application user . It can be one (middle tier user) or more. This schema has the minimal privileges as possible.
• <App>LOG - contains log and audit table per application This schema has a minimal privileges . It's primarily use by field engineering personal.

Terms and meaning :
  Module - A logical unit which perform several business actions.   Application - A set of connected modules    

Here are my questions :  

1. What do you think about the design ? Are there any standard design which I can learn from ?
2. What is the best way to implement several environments ? Different databases ? One database with different schema <App>Sys_QA , <App>_Sys_Prod ? And then to use private synonyms to point to the right schema ?
3. Any comments , or suggestions will be gladly welcome.

I will collect all the answers (if there will be any) and I will put a summary of those later.  

Thanks for the effort .

Amihay Gonen
DBA,
972-3-9268280  

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