If I could write my own version the Funlands here is some of the things I would do. King Kid's full title is actually King Kid the Second, as the first one was still killed by the seven deadly sins. Funlanders only live 18 years, when they turn 18 they explode into confetti, then a few of those confetti pieces "grow" into new Funlanders. Whoever rules the Funlands and has the royal scepter is exempt from the age thing and is actually immortal as long as they posses both the position and the scepter.
In the Funlands what King Kid says goes, including if Captain Marvel can transform or not. He is less powerful outside his realm.
King Kid can only use his powers at their peak if his subjects are having fun. The less fun they are having the weaker he becomes, inside or outside the Funlands.
King Kid still does not trust adults, but will kick them out of his realm rather than enslave them.
King Kid keeps his throne because no other Funlander wants it.
The current King Kid viewed the previous one as a big brother figure and still mourns him to this day.
I love all of this!
I love the way you built upon the world set up in the comics to make something more fleshed out. And your version of King Kid sounds so interesting and more complex. The additions about how and why King Kid's powers work really help make the Funlands more distinct. Yes they have a ruler, but he is powered by fun and the happiness of his subjects so he doesn't abuse his power the way an adult would.
(I have to admit laughed out loud when I read the 'they explode into confetti on their 18th birthday'--it's funny, it's tragic, but I bet that they throw huge parties for those that are turning 18 as a sort of goodbye)
I would love to see your version of the Funlands!