Perhaps, the sail could modulate the reflected beam? That way, all of the heavy communications gear can stay in our own solar system.

Instead of trying to stop at the destination, you could instead send a stream of these tiny expendable probes past the target. Each one would get, say, a microsecond to take a snapshot, and then it would spend the short remainder of its life relaying the raw data.

To do a chemical analysis, some probes could be sent on relativistic collision course with the subject planet, and other probes could watch the impact. It would be a scale-up of NASA's Deep Impact mission from 2005.