Okay made some progress and I may have an answer for you on vmware-fdm. I created a custom ESXi 5.1 image combining the June driver set and June utility bundles, minus the hp-ams package and did a statefull install successfully. I have a support ticket open with HP to find out if they will support this combination, which is compatible with SPP 2012.06 firmware. The documentation for the June release sets does not explicitly state that ESXi 5.1 is supported.
Anyhow when I looked at the software packages included in the base image profile for ESXi I did not see vmware-fdm included. However my BL460c G7 with the custom ESXi image installed is part of an HA cluster, so when I ran the following command from the shell I found it had been installed:
# esxcli software vib list
We then tried booting the host using Auto Deploy stateless using the same image. I noticed the boot and host profile application process slow down on the vmware-fdm package, which is most likely getting installed on the fly as the host boots. /var/log/esxupdate.log shows the package being installed on the stateless host. In contrast, when I installed my image on a host that was not added to vCenter yet, it reported errors looking for vmware-fdm in esxupdate.log.
Doing some research, I found you can include a software depot URL hosted by vCenter itself to include the vmware-fdm package in your custom image:
Add-EsxSoftwareDepot http://VC-Address/vSphere-HA-depot
Add-EsxSoftwarePackage -SoftwarePackage vmware-fdm -ImageProfile profile_name
So next I will add this VIB to my image profile and update Auto Deploy to see if the host boots faster. Please try the same and let me know how it goes for you.