When it comes to content modelling and author experience in Craft, one thing that I keep getting hit with is a lack of a sections field, like the relations fields for entry, assets, categories etc.

I think that could be very useful in a variety of cases. Example: I may have a section and I want to have an index page for that (pretty common scenario). I can define this relationship in various ways, but none of them is as flexible, dynamic and easily managed as a relational field.

A relevant example of such functionality, can be seen in the concept of "mounting" in Statamic, where you basically assign a section to a given page. In Craft this could be even more powerful, because with a relational section field you could corelate a section with any number of pages, so, if needed, you could have many different indexes.

Bonus: I think that it wouldn't be difficult to implement in Craft. The UI is there, and the logic is mostly there.

I would appreciate any comments, especially from the Craft team!