What is the problem with using freeze or bounce to track?
This will record any randomness as well.
Are you doing manual adjustments to the VST while the song progresses? That's the only issue I can see that you can't do this way. You would need to record/write the adjustments as automation, then freeze/bounce...
What am I missing as an issue here?
If you really need to record the output of a vst to the input of another track, I believe you could use a loopback driver. I seem to remember such from long ago. It basically does what a cable from output to input would do...
Keni