Parameterize the Slack user ID?

We created a simple Slack app that uses the Teamcity API to trigger new builds. We've also added Slack notification as a build feature in the configuration. This all works, but I would now like to use build configuration parameters (like eg. slack.userid) to pass along from the API and have the notifications go to the triggering user instead of a predefined user. However, the setting Channel or user ID in notifications set up does not seem to accept configuration parameters.

Is there some other way to handle this or should I report this as a feature request?

Thanks!