I'm working on a plugin that uses view.add_regions(..., ..., scope,...) to add visual information, where I would like to use a "scope" name which would not present in a standard theme file. The only way I know to make this work is to have the user of the plugin edit his/her favourite theme to add the appropriate information. I would like to do this in a more flexible way as follows:
if the scope name is defined in the theme file , use it, otherwise "create" such a scope programmatically - something like:
view.add_regions(..., ..., scope, ...)
view.add_regions(..., ..., my_scope, ...)
where my_scope is a way to assign a given foreground colour. 
I have no idea if it is possible to do (in a plugin) either  or  or both... but it would be really nice.