It would be nice if XrmToolkit supported the concept of versioning workflow assemblies in Dynamics. If you increment the major or minor build number of a workflow assembly, you can register a new copy of that workflow assembly with that new version and then switch over the workflows to the new version at your leisure. Here's an article on how it works: https://docs.microsoft.com/en-us/dynamics365/customer-engagement/developer/workflow/update-custom-workflow-activity-using-assembly-versioning