Could Michigan and/or Wisconsin retroactively change the EV allocation to proportional or by CD prior to the meeting of the electors in December? Serious question, because I recall the Florida legislature threatening to assign their electors to Bush by legislative action if the recount didn't stop.
When you cast a ballot in a presidential election, you're really casting a ballot for a slate of electors. While a Michigan voter might check a box for "Hillary Clinton," theoretically they could look up the list of the names of the group of 16 electors that they're actually casting a vote for.
I think the problem with this particular plan would be that the people of the state would have already cast ballots with the understanding that they were casting a ballot for the whole slate of electors. You couldn't retroactively pretend that the voters had cast a ballot announcing a preference that some proportion of those electors be chosen, or that they cast a ballot for one particular elector retroactively assigned to their congressional district.
Now whether a state legislature could retroactively ditch the election results and assign the state's electors to the national popular vote winner is another question entirely...