Assuming that a vendor customized ESXi installation image is available which contains all required drivers, you can easily update the host from the command line. For this upload the vendor customized Offline Bundle (.zip file) to a folder on a datastore, put the host into Maintenance mode and run the following commands:
esxcli software sources profile list -d /vmfs/volumes/datastore/folder/offline-bundle.zip
esxcli software profile install -d /vmfs/volumes/datastore/folder/offline-bundle.zip -p <profilename> --ok-to-remove --dry-run
Note: Using "--dry-run" will not apply the patches, but only show what would be done. If you are fine with the command's output, run it again without "--dry-run". The "profile install" option will do a cleanup, i.e. will remove any vibs, which are no longer included in the offline bundle.
If the upgrade completes successfully type reboot to reboot the host
André