Consumer sensitive expiration of topic

Hi,

I'm playing around with Kafka with the idea to implement a general purpose message exchanger for a distributed application with high throughput requirements (multiple hundred thousand messages per sec).

In this context, i would like to be able to use a topic as some form of private mailbox for a single consumer group. In this situation, once the single consumer group has committed its offset on its private topic, the messages there won't be used anymore and can be safely discarded. Therefore, i was wondering if you'd see a way (in the current release or in the future) to have a topic which expiration policy is based on consumer offsets.

Thanks,