ESXI Datastore on Guest VM

As the title suggests I am wondering if anyone has any experience attaching storage to an ESXI host from a gust VM. I have FreeNAS running virtualized on a host in my cluster serving iSCSI to my other hosts but I would really like to make that datastore accessible to the FreeNAS host as well, not for primary storage but for the occasional vmotion if I need to bring one of the other hosts down.

Ideally this would be using virtual adapters on a virtual switch and not something hackey like passing through a nic to FreeNAS and connecting to the vmkernal adapter with a patch cable.

I had read previously that it isn't possible but some postings have made references to this being possible in 6.0 without going in to specifics. Hoping someone has those specifics.