Comment 2 for bug 712204

I don't think adding the read-only option is a good approach here. The recipe should rather support a custom-database option to provide the entire database snippet. With file storage, ZEO, RelStorage and various blobwrappers or storages for these, there's too many options that influence those.

It's actually much more explicit and clearer to write the entire storage snippets inside the buildout.cfg (with variable replacement for the directory base parts). Replicating the nested storage config in a set of flat buildout options is just confusing for any non-trivial case.