Insightful. But aiming back would be all kinds of hard. There's very little time before your contraption stops reflecting due to being burned by the unreflected portion of the initial beam.

A retroreflector does not require aiming nor moving parts, it simply uses geometry to ensure that a lightbeam is always reflected back to its source. Retroreflectors are cheap to build and well-understood.

It is a very interesting idea, the reflectors likely will burn but you could cover the missile with them. You only need to reflect enough to disable/weaken the emitter.