I think that the periodicity of payment (weekly in your case) likely influences your proposal to engage casual labor in regular work activities like production and the questions associated with casual labor.
The literal meanings of the word "casual" include temporary, occasional, irregular, etc. When it qualifies the word "labor," it encompasses the nature of the work as well as the periodicity of the worker's engagement. In short, when a workman is engaged in an occasional job intermittently, he is called a casual laborer. Therefore, the mode or periodicity of wage payment is not a determining factor for defining casual labor.
The negative aspects of casual labor include the flexibility of hiring and firing, denial of the benefits of regular employment such as occupational wages, leave benefits, job security, terminal benefits, etc., which result in the emergence of a new social class called "Precariats." Thus, engaging casual labor in regular work activities within an establishment is considered an unfair labor practice and is therefore illegal.