The most well known of those is Shor's algorithm and yet it's still extremely difficult to scale. The problem is that quantum computers, like any quantum system

The most well known of those is Shor's algorithm and yet it's still extremely difficult to scale. The problem is that quantum computers, like any quantum system, are so difficult to control without introducing massive decoherence (EDIT: mixing with the environment and thus destroying any relevant "quantumness"), that they are almost impossible to scale. It is indeed interesting that it's even theoretically possible to create quantum algorithms that are better than classical ones, but that doesn't mean it's practically useful. The latter is the relevant metric for bothering with "the assembly line". What you are talking about is still firmly within the realms of academia.