Spirit System

For whatever reason HW decided to not include BEC voltage in their telemetry like all the other ESC mfgrs.

Would it be possible to take BEC voltage measured direct from Spirit and send that as telemetry value when HW v4 telemetry is selected?

Unfortunately this is not technically possible.
But good thing is, that you can usually get this voltage directly from the receiver. Probably all telemetry capable receivers allow this.
So you can do so in this way and problem will be sorted.

If you are using Spektrum telemetry, you have one port available on the receiver which can measure any voltage.