BB's plan requires Catarina to transform into Saturn and do something and somehow not get caught.
All the Gorosei and Imu would know Saturn is dead, so should the HK. So should the VA and admirals and Akainu...
Literally whatever plan it is, it should fail.
Highest form of authority can control seraphim.
Here's how we can predict things go from now on with that plan :
-BB waits until the Mariejoie situation gets out of hands -> proposes to the WG his help against pirates in exchange of hachinosu becoming a country.
-Revs attack ? BB is sent against them but Shanks is there, we get BB against red hair pirates.
-BB gets access to some marine places, also easy access to fishman island (Poseidon) and takes control of all the seraphim with Devon, betrays the WG again bcz Imu doesn’t know Saturn got copied and underestimated BB.