Can I build my own Content Management System?

Yes you can, but why would you? You have better things to do. 

And it is a lot of work - and nobody knows this as well as Revize Software Systems. Revize Software Systems created Revize with a complete set of practical features in response to real customer requirements including Global Updates, Workflow Management, Scheduled Publishing, Archiving/Roll-back, Audit Reports, etc. 

And on-going maintenance needs can be a nightmare of costs and disruption of priorities as Users will always want more capabilities and new versions of server software will always require modifications and testing.

Web CMS

Revize