The problem with your scenario is that the President can’t impose a settlement on the railroads and the unions. Only Congress can.
Technically he can’t but right now the Democrats have total control of Congress and the Senate, he could put forth a solution to Congress that would very likely pass.
Everyone is looking for political cover instead of stepping up and proposing a solution. If Biden sent Congress a solution to the strike, the Democrats would go along because it’s Biden’s solution not theirs.
Biden wants no part of forcing a solution, if the strike happens and the economy really stalls, he can blame it all on Congress instead of his lack of leadership.