would it be possible to tell it to start
No. A plugin cannot start Cubase/Nuendo.
It might create a remote control interface for that, but then you would have to install scrips etc. Given the Q&A requirements it would take ages to release it.
But even if that were possible, it wouldn’t work. Provided we could tell Cubase to start and then? You say “Pause”, but there is no such concept in the Cubase transport. It is either started or ‘stopped’ - actually it is never ‘stopped’, it is always paused (preloaded etc and is ready to be triggered).
And even if there was a pause function, you never know when such commands as start and stop (or pause) arrive at the process that initiates it, unless you use clock sync. So it would be wild guessing as I said before, and there would be a count-in and then ‘somewhen’ after that, the Performer would hear playback. And that difference between ‘right now’ and ‘somewhen’ can be quite distracting.
what if cubase cycles the first two bars but only starts recording the second time.
Great idea. However not even Cubase provides that functionality, and even if it would, there is definately no way for a plugin to suggest to it to do that 
But it could also just be that you record enable or record disable for the mp3 stream as well
But you can do that afaik, disable recording for that channel in the recording mixer which defines what is beeing sent from performer to Studio. However then you can also not hear that channel anymore.
I may be mistaken, don’t currently have the time to check it thoroughly. But if you disengage the record button in the RECORD section for that ‘talkback’ channel before you start recording, it should be left out of the stereo stream, and you wouldn’t hear the ‘talkback’ leakage. Or use the record level which defines how much of that signal is transmitted and mixed into the stereo stream. There is just no provision to automate that task.
Hope that helps.