One thing to keep in mind is that while you can transparently move data around in cmode, it's at the volume level. You may need to put some thought thought into which qtree you want to group together as in cmode they will move as a group (volume level).
If SnapMirror is licensed on your 7-Mode controllers you can consolidate qtrees from several source volumes on one destination volume via qtree SnapMirror (QSM).
Please note that you will temporarily require additional disk space as the data is copied from one volume to a new vol. Also keep in mind that a downtime is required to perform the cutover (break the SnapMirror relationship and re-create the CIFS shares / NFS exports pointing to the new volume).