Okay, after spending ages fixating without contributing, here's my take:
Antagonist: Dunno witch species but a self-proclaimed Demi-God/ess [of insert ancient empire] with not much to back up his/her villainy. As a result comes off comical.
"The Mumbo":It'd be cool if this character was a ringtailed lemur (perhaps wearing a skull), possibly with a dislike of Laylee. Given his species' nocturnal, it may justify the character napping when you enter his tree (found in over half the worlds, all worlds in Twooka). Not sure what about his tokens, maybe fruits with his face pattern/shape?
The "Jinjos": Different species of parrots?
Fast travel: Stumped on this but perhaps burrows?
The "Chuffy": As a nod to Project Dream it would be cool if you acquire a pirate ship after defeating the boss of a beach level. Consequently most worlds and over world would need to feature open bodies of water. In hindsight I guess I've been playing to much AC Black Flag, but hey!
That's all for now...