The system provides a "Transfer Ownership" functionality, which you can find on  Administration > Users and clicking on "Transfer Ownership" on the toolbar highlighted below. 

After clicking on Transfer Ownership you will be presented with the following. Where you will need to specify which user to transfer From and To which user, with the sections/data that need to be re-assigned.

This will ensure that before a user is deleted or account is deactivated all their responsibilities are allocated to someone else, so they will not delay approval processes.