Not to mention that Cuban isn't exactly a model of tact and decorum. So replace Trump with TrumpLight. Most excellent plan
I wouldn't mind people trying to get someone to run third party if that person actually has a chance of winning AND that person is better than Trump and Clinton. The last criterion is a very low bar though. I don't know much about Cuban but I can't imagine that he could be any worse than Trump, and certainly not Hillary. If he did run as a third party candidate I don't see the prospects becoming any less a Hobson's choice.