How do i get full capacity from Fusion drive on vmWare ESXi 6.0 Mac Mini 7,1
The ESXi 6.0.0 update 2 solves this problem. The Fusion disk is recognised as two separate disks (which they in fact are). With that, i now have two datastores, one on the SSD and another one on the HDD.

What i usually do is install the guests on small virtual disks on the SSD datastore and give them a larger chunk on the HDD datastore. I've also successfully used Linux LVM to extend partitions on the SSD to "continue" to the HDD, but that's for another StackExchange question.