If I understand correctly, what you want is production data with a specific policy and the archival data with another policy. Is that correct?
It is true that this doesn't work today and I don't know when we are going to support this. But we do take note of it. My question however is if you can't take those archive files in the same policy. I assume that they don't change that often so after the initial full backup, the additional overhead should be very small?
Let us know