What I always wanted to try, but didn't have a system to play with, was to change the target pool for migrations, each in a different library. One day nextpool is TAPE1, the next it's TAPE2 - easy enough to update along with the migration thresholds. On a restore, the data would be split between the two libraries, so more tapes could be mounted for a restore process. That, with a high resourceutilization on the client, could give a benefit.
Again, just an untested theory. Nick Cassimatis