Have you looked at http://schema.org/docs/schemas.html and the examples there?
Everything in the example given is encapsulated by schema.org and that would describe it in a way that was unambiguous.
I know that schema.org has been dismissed because "The problem is that it's too complicated for a non-developer", but I would say that for a non-developer this file is also too complicated. Most non-developer small business owners can barely use FTP or use the Wordpress admin. These people don't have a robots.txt and won't create a business.txt
I would argue that making business.txt schema.org formatted and then to use a simple generator wizard to produce it would be more accessible to the small business owner than giving them a text file to edit.