A broken padlock or even ongoing broken padlocks doesn't invalidate a good idea.
Almost everyone breaks the speed limit, speed cameras are vandalised, yet it's a still good idea to enforce speed limits.
Any system will require some ongoing maintenance/resources to ensure enforcement/compliance.
Given: 1. The system is already in place 2. all boaters have a key, 3. replacing padlocks, chains and gate locks are relatively cheap it strikes me as the cheapest, most cost effective and non-disruptive solution.