we run a manual export.
First we make collections for Onboard Admins, then servers with seperate ESX, Windows and Unix lists. Then we use the report function to export these collection. We document the credentials and export you collections install a fresh SIm set all credentials per job paste the objects that these credentials can discover and start with the OA. Then the OA discovery adds the ILO's and switches. Then we add the servers. If all goes well you can be operational again in 2 hours. And you still have the old server running so no real outage.
This seams like a lot of work but if you document a dry run you also have a worst case doc...