Moving snapmirror relationships to a new pair in CDOT is not difficult. If you have old pair A (prod) and B (DR) and new pair C (prod) and D (DR), you enact the scenario like this:
Create new DP volume on C
Create new DP volume on D
Initialize A > C
Initialize B > D
Discontinue access to A.
Create a named snap (i.e. "syncsnap") on A.
Update A > B using this snap as the -source-snapshot.
Update B > C using this snap as the -source-snapshot.
Update A > D using this snap as the -source-snapshot.
Break/delete the snapmirror from A > B.
Break/delete the snapmirror from B > C.
Break/delete the snapmirror from A > D.
Create the snapmirror from C > D.
Resync the snapmirror from C (source) to D (destination), using the named snap (i.e. "syncsnap") as the -source-snapshot.
The relationship will resync without re-baselining needed.
Alternately, prior to this, you can update the A > C and B > D relationships using previous snaps as the -source-snapshot parameter, if you want/need to maintain the snapshot chain.