Possible to dual boot between VMware & Server 2016?

Why? You can just run Server 2016 under vmware... It really doesn't add much overhead...

It's not recommended, as ESXi is a Bare Metal OS, and the VMFS partition cannot be read by Server 2016. I have seen UEFI BOOT solutions, which can BOOT either, but you need a custom Boot Manager.

Decide if you want to use ESXi or 2016 (Hyper-V)

This will be setup where VMWare will be installed on a separate array from the Server 2016 server OS. Neither OS will try to read from the other's disks.
This will only be setup on a test system.

still need somewhere to write the boot loader...