After creating subdirectories for per-user galleries and pointing CE to them, we are able to restrict the file picker to just those folders, and now templates works by not using the Security Prefix.

 

One of the things we've noticed is that The file picker can be a bit sensitive. It won't list templates with an embedded space in the file name. To make this component friendlier to users wishing to compose emails (and email templates), it will have to be more friendly, or users will have to be explicitly trained not to use spaces in the template file name.

 

We are happy with it so far, and hope to get all of the requirements fully fleshed out. At the moment we are going to investigate custom buttons and menus to see whether it will give us the customization we need to allow users to pick read-only public templates.