I think the new Template/External system is great as it is. It just takes some thought, planning and organisation to get the most out of it.
In the future, it would be the final icing on the update cake if users could add small screen shot images of the Previewed layout to Templates/Externals so users could inspect or search visually. This would be a next level improvement on the current text only descriptions.
Here is an example of the type of thing that BootstrapStudio and others do - see below:
So, in the screenshot, the list under Downloaded, in Stacks, could be the Templates, and hovering over a Template would create the popover containing a screenshot of the Template, name, description and in this case Author with a link to the Author (if relevant).
I think this would take Stacks into a new area where developers could deliver demo and example Templates. Such a system could have a Help link to the stacks used or Template help page.