Using TinyMCE templates in Plone 5 is supported be default.
See the theming training for an example:
But we need to provide some good templates including the corresponding css for it and we need to enable the TinyMCE template plug-in by default.
With this we can provide useful static HTML blocks, the user can add and customize later.
This could be a 2x2 teaser grid or just some pictures with labels or any other often used content structure.
I would suggest, to create a packaged for now to test the layouts and later integrated the idea and the best templates into Plone core.
This can even be useful in combination with Mosaic. Users can add static blocks into Text Area tiles, customize them and dragging them around with the Mosaic editor.
What are you thinking about this?