ManagerManager can do this with the following rule...
Turn rich text off by default
mm_default(’richtext’, 0);
Turn rich text on by default
mm_default(’richtext’, 1);
In Revo, yes, you can do it for individual User Groups, or by "constraints" (like a Template or context_key), via the Form Customization section.
Would that be settable for individual documents, document groups, and specific parts of the site (i.e. inherited from the parent)? Otherwise, it just does what the system setting does.