Not really. Nnot like you can change your keyblade to something else, know what I mean? I say factions but I really mean where you belong in terms of weaponry, its a fight against light and dark so technically Keybladers and Wayward Travelers are on the same side, they'll join up. But if you mean that you're an evil Wayward Traveler/Keyblader, you should be starting with the Dark Apprentices. Or I mean if your character decides the light dudes are lame and want to join up with Maleficent, then sure, you can change sides. Just note it's easier to go from light to dark then to go from dark to light.