So you're saying that even if I get the vmkfstools -z or -r setup to work for my HDDs, it will not be supported?
Yes.
(b) a bit of performance
The performance hit related to virtualised disks is a Hyper-V related myth. On modern ESXi systems, I never seen a benchmark show a determinable difference (excepting of course, the "I build two high load VMs on one host and they performed slower than on dedicated hard" scenario).