You can use a combination of PPRC extended distance and FlashCopy® operations to create a consistent copy of the secondary volumes using the procedures described in Scenarios using PPRC extended distance and synchronous mode for backup purposes.
Guideline: As you plan to use PPRC extended distance for point-in-time backup solutions, ensure that for each PPRC target volume that you use in each LSS (at the secondary), there is a another volume (physically) present in each LSS in order to facilitate FlashCopy operations to target volumes.