I will develop a sharepoint document repository with multi level approval flow

This comprehensive repository has the following features:

• Read only mode for all documents.
• Separate Views for current and obsolete documents.
• Expiration date for each document (optional), c/w notification email to the document owner prior to expiration date.
• Buttons visible only if you are the document owner and the document is not already "under review":
• Button to submit a document for review/update, c/w "assigned to", due date, and "requirements" fields.
• Button to edit metadata.
• Email notifications at every step of the process.
• Document status changed automatically (less Obsolete, which is done via Edit Tags button).
• Revision history auto-fill.
• Daily email notifications for documents under review with past due date and for documents scheduled for periodical review.
• Daily check in of files left checked out overnight.
• Multiple Libraries with status of each document and restricted visibility for users,
• Complete automation of the system with buttons set for emailing, editing metadata and transferring documents between Libraries,

Further expansion to accommodate more (or less) approvers is available.