Whether your D&D5 paladin is an LG or a Motorola paladin, I sure hope you weren't planning on using the digital tools anytime soon OH SNAP YES I WENT THERE
I've always been of the opinion that you can vastly oversimplify alignment by saying that a character's ethical alignment refers to their means and their moral alignment refers to their ends. My stance on alignment restrictions for classes has therefore always been split.
I think there's a genuine validity to, say, monks or paladins being lawful, or barbarians or rogues being chaotic, because these classes use lawful and chaotic means to reach their ends, respectively. You could argue that to death, and I am not saying there are not ample reasons why that is not necessarily the case. I'm just making the case that there is some justification for it.
But the idea of morally bound classes doesn't sit as well with me. I don't even really see assassins as necessarily evil. Chaotic, yes, because of their means, but every D&D character kills with relative impunity. The difference in the assassins case is that he does so in "inappropriate" circumstances that could land him in prison if he is not careful.
Depending on the assassin's method of target selection, there's no reason why he couldn't be just as "good" as the fighter who kills his way through a bandit camp, if, say, he creeps through Waterdeep killing crime lords in their sleep.
So, long story short, I'm glad there will be paladins of many alignments (again) in D&D5, but I hope that the designers considered the fact that a lawful paladin and a chaotic paladin should have access to very different abilities and reflected this in subclass design.