What about:
defining a new deviceclass,
using this deviceclass in a new storage pool,
defining this storage pool as next stgpool for the old stgpool,
updating all copygroups to the new stgpool
lowering the migration levels of the old stgpool to hi=0 and lo=0

With this method all is done automatically without specifying a move data for
every single volume in the old stgpool. Moving data for lets say 600 volumes
would be an enoying job.

Michel