i doubt kuma is similar to moria, crocodile (former shichibukai), and doflamingo's intentions. he would be more like hawkeye. he doesn't [yet] have a laugh same with hawkeye. plus his role to the moria arc would more likely be the same with aokiji, as a major arc instigator or something. i think kuma's more on the good side of the WG and he said before he has a news for luffy which i think is about ace. if ace is dead or captured, naturally his grandfather Garp would have known it immediately. and if his real intent is to kill all of them, he could easily start with luffy while he's still unconscious as for sometime now is being visually emphasized on the manga upon arrival of kuma. i thought before his power would help them reach merman island which underwater. now, i think that would be of different way than teleportation. and since the introduction of kaidou, a yonkou, having another shichibukia as an enemy in the next arc would be too much of a repetition. kaidou could be a starter for the strawhats leveling with the power of yonkou as crocodile was with the shichibukai.