Because if your plan succeeds, and Trump falls just short of the majority, and the GOPe selects Ryan or Kasich or Romney, Hillary will win in a landslide. Not just because so many Trump supporters will be angry and not show up, or that the cross over votes that Trump gets won’t happen, but because it will just be another GOPe loser that can’t get any states that Romney didn’t get last time.
Sorry, Trump is going to have to win the nomination the old-fashioned way - by winning the most delegates. If he can’t, that is on him - not on the people that won’t just get in line when he says so...