Can you provide a little bit more information about your goal of “not forwarding” topics. If they don’t have a matched subscriber on the other side they won’t get forwarded.
You can relatively easily remap any topic to a non-matching topic and it won’t get forwarded.
For your example of throttling a topic there’s already tools for that like throttle you’ll end up publishing the data at a slower rate on a different topic and remap that to connect to your ROS2 system.
In general I do not believe that we want to support blacklisting topics for the bridge. If every other topic passes through but one topic doesn’t, if you didn’t configure the blacklist yourself it would be very surprising behavior and break everyone’s assumptions about connectivity.
Your use case is more general than just the bridge which is having tools to selectively expose lower datarate representations of robot data externally. There’s been lots of though experiments and we plan to attack this sort of tool in the future as the new QoS features will help it a lot too. This tool can be written to run on either side of the bridge. But we expect that the introspection and orchestration APIs in ROS2 will help with this tooling a lot.