It's surprising that opponents of the direct election of the president dwell on the intent of the Framers. These drafters of the Constitution plainly invested the states with the authority to decide how to allocate electors. See Article II.
The question then is: how should states exercise that authority in the best interest of their citizens and all the citizens of the United States? The Framers made some interesting comments about the choice of the president, and they are worth revisiting. But there is no doubt the manner of choosing electors was left to the states. They can change to any method they like, as long as they are not running afoul of some other provision of the Constitution.