Immigration reform is far more important that a wall. Immigration reform is medicine, the wall merely a Band-Aid.
As for a federal holiday on Election Day, I'd be in favor of it IF coupled with an end to early voting and mail in voting. Like you said, those practices are recipes for abuse. Let everyone show up physically at the polls on Election Day to vote.
I'm against it, because it would be a
Federal Holiday. That means it would only apply to employees of the Federal Government. The only votes this would encourage would be the votes of Federal bureaucrats, giving them a voting edge over the rest of us minions who work in the private sector. As if they needed more incentive to screw over people who have to earn for a living.
McConnell is correct on this, but because it goes against the grain of the Leftist media, he will cave. He loves them far more than he loves us.