I’ve been remiss in not announcing this over the last few weeks. Starting in User Management module versions 15.0.59 and 16.0.25.12 is a new feature that allows Admins to enable rules for minimum user password complexity.
Browse to Admin → User Management → Settings tab → Authentication Settings sub-tab
You can toggle individual rules as you wish, and there is a field at the bottom for testing. These rules apply when a user changes their password in UCP.