Deleting the tests will not impact coverage as the tests at the integration points will necessarily already cover any local functions. That is unless said local

Deleting the tests will not impact coverage as the tests at the integration points will necessarily already cover any local functions. That is unless said local functions are unused, but in that case you would remove the unused local functions anyway, still not impacting coverage. But you are right that deleting the tests isn't an option as it will break the contract that was entered into with the users of the code. Of course, you can't modify the tests for the same reason, so...