Thank you for a very useful run-down.

On the Fourteenth Amendment case, a conservative super-majority would support a state's right to boot anyone off the ballot for any reason not covered by an affirmative protection of the Reconstruction Amendments. There is no other federal law at all on who may be on the state's ballot. So long as the electors are appointed in a manner determined by the state legislature, the Feds have nothing to say on the matter.

In case SCOTUS is unsure, I have written an opinion they can use.