Hi,
I have a feature suggestion for vSAN, dunno if it has been mentioned earlier, but I thought I'd air my thoughs on these forums, and if it seems promising I'll try and send a FR through the proper channels 
So, my thought is based on customers wanting both cheap storage and fast storage, sometimes for the same VM (OS on fast, with an archive disk on slow/cheap storage).
The idea is to allow vSAN nodes to provide disk groups for two different vSAN datastores, essentially supporting both all flash and hybrid mode at the same time, on the same node.
If it's not possible to do this within the same node, perhaps it could be done within the same cluster - different nodes providing storage to different vSAN datastores. As long as all nodes are in the same cluster, VMs should be able to allocate storage on both vSAN Datastores.
I think this would be a great addition, that way we can nodes with 3.5" 8TB+ drives for those massive amounts of data, and provide it much cheaper than using flash drives for this as well.
Hit me with your thoughs and suggestions!
/Andreas