Not enough states will pass this BS for it to ever take effect.
And even if they did, it is unconstitutional and would not stand up to judicial review. Non-issue.
Hopefully, as you stated, enough states will reject this. However, as more liberal human waste infests the sane states, this could be a problem that sadly the Supreme Court will have to deal with. One one hand, the Constitution says explicitly that states can choose Electors in any way they see fit. Furthermore, interstate compacts are allowed. On what grounds does this proposal become unconstitutional?
Please note I am not trying to say this is a good idea. I think I might be missing something in the Constitution that disallows this.