How to rename objects such as virtual servers

you could leverage journeys tool and run through a manual migration but not actually complete it.  During the process there is an opportunity to edit configuration objects names etc. and if you opt for an offline migration, it will create the new config file with the adjusted names etc..  This is not the main use case for using Journeys, but the tool does allow for object renaming when preparing for config moves / TMOS upgrades.  Journeys