I expect Marco will fulfill the role of the pheasant and go help Yamato,Momo and Luffy
by the way Momotaru'r role is not displayed by Momo alone but by Luffy as well
Momotaru = (Momo)nosuke + Luffy(taru) so Luffy fulfill two roles being the Moneky but as well half of Momotaru.
Yamato is the the dog here . If Oda acts straightforward then Marco is the pheasant but if not
then I expect him to give this role to Sanji if he really transforms into a bird himself. if Sanji go help as well then you can be sure that Zoro will help this time against BM.