If I followed correctly, Trump's campaign is raising equal protection issues in PA. Apparently, the law allows curing of mail-in ballots. If signatures or secrecy envelopes were missing, election workers contacted the voter to 'cure' the mistake. However, some workers in some Republican precincts were unaware this was allowed, and treated them as spoiled ballots. The Trump team claims this violates the equal protection clause.
I see a few major holes in this this argument. First, curing ballots is legal in PA. Guidance was sent out to all the precincts. There was no fraud.
Next, the 14th Amendment guarantees equal protection under the law, not equality of outcomes. Clerical errors do not amount to loss of equal protection under the law.
Finally, election laws already vary widely from state to state. For example, some states require voter ID. Some do not.