I hate the idea. But I think you're right. The Constitution gives the states have great latitude in how they assign their electoral votes.
So folks need to take this threat seriously.
The only remedy is for another state to sue based on losing thier weight in a weighted election. They could show damage based on the the assignment of electors which prevents this in the first place.
Interesting that the intent of the founding fathers was for state legislatures to elect the president.