In re-use mode, data only moves to the ECC table after activation. So, during approval, everything is stored in staging tables that you should not have to worry about.
So, I would definitely recommend a "re-use" implementation of your custom ECC tables. You have to build an "access" class that will handle moving the data eventually to the actual tables when the CR is activated.
You should always consult this page for any MDG questions: Configuration and Enhancement of SAP Master Data Governance
This document (can be found in the above page) addresses your question in more details: http://www.sdn.sap.com/irj/scn/go/portal/prtroot/docs/library/uuid/80cfacff-803f-2f10-ec92-9af0dd9fd89e?overridelayout=true&55563991929909