Most customers using DRS configure only "run" and "default" rules while avoiding explicit block rules.
This way they can add additional rules using ESL in case of urgency. It is often not possible to 
quickly change the DRS rules as they must be validated, tested, signed and deployed. This typically 
takes a week or more. In particular signing is often a bureaucratic process in many companies. 

DRS does support a customizable message as part of blocking rules only. The enhancement 
request is to add such a configurable message also for default rules. In case an application is blocked by default since it's untrusted then a user could be informed to contact e.g. the help desk.

It is understood that such an enhancement is not trivial to implement as there are many places in the
code where security warnings are being launched. Nevertheless such a functionality should be considered as it's a common requirement by customers today.