Exchange team saw the need to cater for incorporating local autoconfiguration file. In outlook, There is a registry key used to tell outlook to use local autodiscovery XML file. This is particularly useful in migration scenarios. However Lync & SfB can only use DNS autodiscovery. It's worse with SfB, EWS cannot be turned off.
I would like to see this feature as it solves migration issues, without giving users authentication prompts.