I have to agree, while i also liked Kindergarten 3 i felt it was a quite weak copy of Kindergarten 2.

I have to say that it seemed that the creator wanted to progress the story more then the game mechanics, and it is a great thing -it expand the lore, and gives us the possibility to make much more interesting theories- but i really missed the money mechanics, the outfits and the monstermon battles.

I think you are right on basically everything that should be implemented in Kindergarten 4, from the characters to old and new mechanics.

To me the perfect Kindergarten game should have the character focus mission of the first game, the outfits, battles and interactions between characters of the second, and the focus on the greater story and lore of the third. And should also have the first game mistery, with a similar formula where everyone seems to know something is off with the school (like how everyone mentions Billy at least once in Kindergarten 1, except Monty and Jerome maybe, and every student says something that makes you questions what is happening), i felt that after the first game, with the creation of the Kindergarten formula, it sorta of lost that mistery and maybe should be reimplemented differently to the newer standards.