a gorosei goes to eddhead just to activate supreme command and use seraphims? It's absurd, if it's a voice command, which it is, just make a call by den den mushi or by den den mushi video and that's it, they're in control without the highest authority on the fucking planet showing up in the middle of a conflict between crews from yonkou and cp0
gorosei is going to capture or talk to luffy.
remember, they were notoriously unsettled by nika's awakening, so they have to go personally
I think we could see something like shabaody 2.0, with the exception that they will not be dispersed but flee
the gorosei will demonstrate at this point that: either they are politicians with only political force or, they are warlike powers
but I don't see a relationship to going only for the control of seraphim