The problem is this. You would hope that a lot of Football League clubs would be against this - but they may not get the chance to vote it down. If 18 of the biggest were tapped up to resign from the FL and be guaranteed a place in PL 2, they would probably do it. Done deal, fait accompli, FL powerless.
I think this is right, it wouldn't matter that 54 clubs voted against it, the top 18 would bugger off.
The only thing that could stop this is if promotion is part of the league's regulations. In other words, is there a legal requirement for the top teams in League 1 to be promoted on the Championship? If so, the PL couldn't just hive off the 18 teams they fancied for the new league, not without a legal battle.