parent/child content modelling

hi all. i've got a content modelling question - thanks in advance!

i'm building a site which is a knowledge-base for our design system. i'm trying to create a type of page called a Foundations page. A Foundations page has no content of its own, but will have a number of child pages displayed as tabs. the tabs will have their own urls, so e.g.

• foundations/typography/introduction
• foundations/typography/patterns
• etc

the url for the foundations page will redirect to the first tab, i.e. foundations/typography will redirect to foundations/typography/introduction.

my question is, how to model this.

i've tried creating a Foundations collection with a relationship field with a hasMany relationTo a Pages collection, which contains the sub-pages. the problem with this is that the pages then are re-usable, and it becomes possible to have a sub page sitting underneath multiple Foundations pages, which i'd like to disallow. it's also not possible to see from the child page what its parent is - potentially confusing to an editor if we have multiple pages with a title of "Introduction" say.

i can do it the other way round - a Pages document could have a relationship field with a relationTo the Foundations collection, but then the Foundations document doesn't know what its children are, and there's no way to order the children from the Foundations document.

the third thing i tried was to have a blocks field on the Foundations collection allowing the user to add the content for each tabbed page as a separate block directly on the Foundations document. this solves the above problems, but it means that the UI becomes unwieldy - the content for multiple (possibly quite long) pages will all be displayed on the same page. the blocks seem to be collapsed by default which makes it better, but if an editor un-collapses more than one it gets a bit confusing. considering everything though, i think this is the best option i've come up with.

are there any better ways of doing this? any thoughts gratefully received

(i did see this nested docs plugin which looks interesting, but i don't think fits my use case because i only want to allow one level of parent-child relation, and because the parent and child wouldn't fit into the same collection)