It would be great if it was possible to  include VST Instruments variations to be saved and recalled via Mix Scenes same as it is possible with Insert Effects . it is already possible to do it by utilising Third Party VST like Blue Cat Patchwork amongst other VST's that can do similar results . included short video to demonstrate it.  this workaround involves few extra steps but it can be done . native implementation would be great ! 

https://youtu.be/_Rfn3EglODM