Conditional Fields / Flexible Content Repeater

The main challenge I have when using custom fields for content is that there is no way to conditionally show relevant fields based on the value/setting of another field.

The main use case for this is that if you add a Field Collection for, say 'Content Sections', each containing a variable number of 'Section' children. Then within that Section it would be useful to have 'Type' as a select field that would then determine the fields that are required.

This then makes content creation much more powerful because basically the type of content that goes in to a collection is flexible, and the order of those sections also much more manageable.

As far as I'm aware, right now to achieve this you're forced to have a Field Collection containing sections with ALL possible fields, then to only fill out the relevant fields which adds a lot of unnecessary field clutter.

Hopefully that makes sense, and if there's an efficient way to achieve the above with the existing features then I'd be happy to hear it.

Another option would be intead of using a Field Collection, a new type of field (Repeater?) that would allow you to define separate nested groups of fields, and then in the admin it appears to the user that they can add a field group of their choosing to a repeater.