Keeping consistent quality of marinated meat throughout the day in a restaurant
Your question is actually a more general topic under food quality.

The concept is either called stock rotation or just-in-time(for manufacturing).

You simply need to anticipate the need for the item and prepare it ahead of time, multiple times throughout the day.  If you need 10 portions an hour starting at 6pm, you need to begin marinating 10 portions at 3pm then 10 portions at 4pm and so on to satisfy your needs for the day.  Your work day begins when prep time must begin, not when your restaurant is open for customers.

Many restaurants do this with any product that doesn't hold well.  These items need to be prepared several times throughout service and rotation is a good way to do it.

Bakers don't go to work in the wee hours of the morning for no reason.  They do it to ensure their products are served at their peak of quality.