How about a plugin to help manage or facilitate increasing individual party members/actors/class's level cap.
Inspiration - Final Fantasy XI: https://www.bg-wiki.com/ffxi/Category:Limit_Break_Quests
In Final Fantasy XI you could only reach a max of level 50 on your character on all jobs/classes. You had to a special side quest that would grant a key item that would increase the limit first to 55, then 60, 65, 70, and 75 (and then eventually to 99 as the game went on) as you completed more of these quests and got other key items. Would it be possible so that if you acquired a key item (or flipped a switch) you could have certain actors increase their max level limit this way. There could be options for either specific actor(s) or the whole party depending on how the user would wish to use it. In my game, I would like the idea of having each party member do a quest in order to increase the level cap.
I also thought of another variant of this using a character recruiting system similar to a Gacha where you would collect party members randomly through a wishing system, and if you collected a "duplicate" then the character you already have will be able to increase their level cap as well.