WIP: Update 3 for !51

docs/CONTRIBUTING.md

@@ -88,11 +88,19 @@ to get started. You will need to:
 
 ### Modifying a Workflow
 
-Workflows will need to be maintained and updated over time as tools
-and technology progress. The best approach to modifying a workflow
-is to recreate steps on your local system (if possible),
-identify failures and fixes, then translate fixes to the reusable
-workflow in question. If you encounter an issue that requires
+Existing workflows will need to be maintained and updated over time as tools
+and technology progress. Workflow modifications will typically be accepted
+only if:
+1. The modification addresses an existing, documented issue in the reusable
+   workflow that prevents the workflow from operating as intended; or
+2. The modification adds a minor feature update that is deemed suitable
+   for integration with an existing workflow rather than the creation
+   of a new workflow. The feature update will benefit an assortment
+   of ITK external modules.
+
+The best approach to modifying a workflow is to recreate steps on your local 
+system (if possible), identify failures and fixes, then translate fixes to the
+reusable workflow in question. If you encounter an issue that requires
 community input you can ask for help on the
 [ITK community Discourse forum](https://discourse.itk.org/).