@Elki
Broadly speaking, you're right in that Baldy's character development will probably be a central focus of the plot. I think it's too early to say if he'll be the main focus though; Prince seems like he'll be getting his share as well. My worry with Baldy is that right now he's a super lamer right now, and although character development is great the boot licking scene is off putting. Yes, eventually he might end up being great, but like many other weak -> strong stories can easily turn into a slog if not done correctly.
Furthermore, due to the nature of the possession premise, if things stay like this for an extended length of time it's likely that we're gonna get a lot more Baldy and a lot less Prince, which is very unappealing since right now Prince seems way more interesting(to me, personally at least). You mentioned that without Baldy the story would be run of the mill, but there are so many 'wimpy kid gets superpowers' stories out that these days I don't know if that still holds.
Not trying to say you're necessarily wrong with your assessment, just that it seems like a lot depends on how the author succeeds in developing Baldy, and if it comes at the detriment of more interesting characters(again, subjective) I would almost prefer not.
Hoping for the best!