Override text/plain MIME type by extension?

[Karmaflute]

I want no-extension files to be executable based on their permissions (execute or not). Is there a way to have these files open in a text editor when no execute permission exists and execute otherwise?

 

I've used Default Apps to set the default application to disabled which allows the files to be executed. But then other files associated with this MIME type such as .txt and .text are also affected. I want these types "by extension" to be associated with TextEdit.

 

Is there a way to do this?