> I just want to be able to run xubuntu 16.x (and newer when it comes out) in Unity mode
Apparently Workstation 12 removed Unity mode for Linux guests because it was rarely used[1] - I'm just speculating (I don't work in End User Computing) but I imagine that was based on Customer Experience Improvement Program (a.k.a. telemetry) data (I know some people prefer to opt-out of participating but the information is useful, we just implemented it in the product I work on and we're looking forward to being able to make better decisions about feature/bug priority based on it).
If you'd like to provide feedback on Unity support for Linux you might want to tweet to the Workstation team @vmw_workstation (and/or perhaps their PM, @mikeroysoft).