You do realize that if there is no majority winner on the first ballot, that the delegates keep voting until there is a winner?
And that in this case some of the delegates will have to change votes, or else they will have ballots until infinity?
If I was going to construct a rule, I'd make it so that delegates are bound as long as the candidate to whom they are committed is one of the top two vote getters on a particular ballot. Or maybe limit it to the top four on the second ballot, top 3 on the third, and top 2 on the 4th, so it couldn't go more than 4 ballots.