OK... let's walk your suggestion through.
The President resigns.
The Vice-President succeeds.
The Vice-President is now the President.
Now the NEW President is obliged by US Law...
to violate US Law.
So we enact your solution again...
The NEW President resigns...
This time the Speaker succeeds...
The Speaker is now the President.
Now THAT new President is obliged by US Law...
to violate US Law.
So we enact your solution again...
Do you see the problem yet?