Template that allows for future layout and design changes to previously created pages

We would like to build a model that allows us to create a large set of pages with a specific layout and design today but we will likely need to modify the layout and styles in the future and we want all previously created pages to be updated in one place rather than having to go back to every individual page.

For example, we would like to build a website that provides information about restaurants.  We would like to create a template for our restaurant detail pages.  Each page will contain a main nav bar, hero image, a title, some body copy that provides a lot of detail about the restaurant, and a component a component below it that contains a list other restaurants.

Our current thought is:

1. We will need to build a template that contains components for all of the above elements.  Those components would be placed either in "Structure" or "Initial Layout".
2. Authors will create a new page for each restaurant using the the "Create" button and choosing the template.
3. Authors will replace "dummy" images and text with real information.

This process will likely be used dozens of times to build dozens of pages.

We are confident that we will need to change layout and change styles at some point in the future.  For example, we may decide to add a block of static "About Us" text between the body copy and the list of other restaurants and we may want to change the style of the title.  We will want all of our pages, including the ones that were previously created, to include this text and update the title style.  Since we will already have created dozens of pages, it would be best if we could do this at the template level and have that change apply to all previously created pages automatically.

What would be the best approach to solve for this scenario?

Thanks.