The trouble with this as proposed is that you would have to send double the data over sACN because the “previz” data would need to be on completely separate universes as your live data. This is just the difficulty in the output and does not address the double processing that the Vista application would need to be doing as well.
Ideally in order to do this correctly the previz data would stay internal on the machine which is similar to how q-view and stealth currently work in the fixture chooser. For now I have to say this falls under the built in visualizer category, not a high priority due to the complexity of the process.