Control usage of wysiwyg

Summarization of http://drupal.org/node/81297 (actually copied from current wysiwyg.module):

Considerations:

1. Take D6 FAPI3 / widgets into account (see #138706 and #86535).
2. Run registration either in hook_elements() or hook_form_alter(). form_alter() might also allow to load needed JS/CSS.
3. Use an attribute or class name or both (editor code analysis needed). Or alter field #type 'textarea' to 'html' (IIRC, suggested by Moshe in IRC).
4. Disable an editor for fields using the PHP input format.
5. D6: Perhaps depend on the input format to *enable* wysiwyg for a field.
6. Allow to take the current path into account.
7. Allow to force an editor for certain CCK fields (f.e. user input).
8. Disable core's #resizable if an editor does not support it.
9. Allow contrib modules to extend this definition.
10. Allow to manually extend this list via wysiwyg settings page.
11. Include an editor profile or user role to limit/enhance available plugins.
12. Take other input formats (e.g. bbcode) into account.