Workers are already at an extremely high level of productivity compared to any other time in history. The problem is what they get in exchange for their labour, and that is a question of monetary policy and how inflationary money enters the economy (it's through real estate).
Going beyond unionization to ownership, one solution is worker-owned co-ops. Making those easy to start and providing tax benefits for such would be fantastic.
Worker owned co-ops have existed for a long time and they don't solve the problem, because they still have to compete on the free market for money that is created out of thin air and distributed through real estate.