Laffitte literally Infiltrated Mary Geoise by himself, so He could have came to Egghead alone without a Ship
And if They wanted to Fight, They would have brought more
But since They brought a Ship, then it was necessary for Devon to come along
So that means, whatever They want to do would rely on Devon's DF
This indicates that They most probably wanna take control over Seraphim
And i assume that if They succeed, They will contact Blackbeard so He comes to Egghead
I'v been saying it for so long that Oda is preparing to Introduce Lurking Legend/Final Villain
And He wants every Faction to witness his Arrival, so that everyone re-thinks their Plans, Goals & who they should trust/oppose
He isn't someone whom only SHs needs to meet
That's why We already have Marines, Gorosei, SHs, Bakkin asking Marco to go there, Neo Mads coming there, Blackbeard Pirates coming there, Morgans is interested on what's happening there, Vegapunk contacted Dragon, Red-Hair Pirates aren't that far ... etc
I hope Oda nail this Introduction & it's gonna be more Epic than other Introductions such as Kaidou's & Mihawk's