Currently, vinyl control doesn't behave like every other means of manipulating the waveform in that it doesn't set & clear the Play status which causes a number of problems, most notably other parts of Mixxx being unable to detect if a virtual deck is playing. This could be solved by adjusting it to use the scratch2 CO which allows direct manipulation of the track speed regardless of Play status, allowing the VC code to set & clear the Play status as appropriate. The only trick then is for the VC code to figure out when to set & clear Play. One way is to sample the timecode speed over some amount of real time and if it's playing steadily (within some margin of error,) it should set the Play status. Otherwise, it should clear it. You might use the running average algorithm as implemented in the common MIDI script file for BPM tapping.
this is fixed in features_xwax2