patterns in character plot power (the ability to effect the plot) in relation to character growth and identity 

One thing I noticed after watching some of the later seasons is that Twilight has gotten much stronger with magic. However she has not gained as much wisdom as I expected, considering all of her friendship lessons and the friendship journal, which has taken a back seat to recent devlopments.

I think this is an odd direction for the writers to take because it sets up Twilight to make silly decisions, such as in the hatfields and mccoys episode, where her standard solutions to a standard problem were entirely ineffective. Perhaps they are trying to setup a story where Twilight has to learn that not all solutions are simple or empirical which is related to the lesson in Feeling Pinkie Keen, but from a different angle, with different connotations, as the lesson presented there does not capture the entire scope of the intended thought patern, which is faith, but independent of belif, a fairly nuanced subject in its own right. I think that currently, such discussion is beyond the scope of the show.  

Considering her newfound status and power it appears that she might have to deal with additional responsiblity (for her subjects/friends), which could lead to a great power/great responsibility type story, which seems possible within the scope of the universe. It also setups Discord to be a contrast of unbridled magical power on one hand and Celestial as magic bridled by order and responsibility, with Luna as the oposite end of the spectrum with magic entirely dominated by responsibility and guilt (Id, Ego, SuperEgo). Restraint and self-control is a topic that has not been discussed often in this series which I find surprising, since all the tools for such an episode already exist, and have been mentioned separately, but the connections have never been drawn explicitly, such as the need to balance work and play. It might be good setup for a multi-episode strip. 

The rest of the primary characters are getting more and more character development and growth, as indicated by their abilities to handle individual problems on their own or without oversight and counterbalancing from the rest of the group, indicated by the map episodes, but I feel that Twilight is not growing fast enough to keep up. Most of her plot power is derived from her magic, which is used to facilitate the actions of other characters and as a result her character growth suffers in order to prevent her from becoming a mary sue type character, which I think she skirted during the end of last season (4), and the beginning of this one (5). It is a dangerous situation and one that can become a problem if Twilight's magic continues to grow, while her character development proceeds at a snail's pace. Some kind of system may have to be put in place in order to limit her potentially story breaking powers so that she can continue to grow as a character rather than as a plot device, previously exhaustion was used, combined with a lack of understanding and "hidden power", power that was governed by artifacts and potential, which limited power to situational times, when it was needed and required to end a threat. Notably artifacts such as the magic lockbox and the elements of harmony have been removed from the table reducing what is effectively "power creep" but the reduced overall creep has brought attention to the significant differences between character power. Rarity previously had a similar amount of power to Twilight but as the series grew, her magical talents began to be overshadowed by Twilights massive power spikes, shown in the end of Season 3, with the alicorn transformation, and somewhere around season 4 and season 5, where Twilight gains more active magic capabilities. 

I am interested in what the writers will do to combat this change, will they hand Twilight the idiot ball to keep her at the same plot power as her friends, or will they give plot power to her friends, as evidenced by Fluttershy's growing animal and speaking capabilities? Pinky Pie exists outside the realm of logic and so is exempt from these criteria, but Applejack, Rarity, and Rainbow Dash are at risk since their abilities are inherently definable and therefore limited. Fluttershy seems to have grown from being a floor mat in the earlier seasons, but effective plot power among the other three seems to be slow when compared with the latent growth of Twilight's magic which is itself rather potent, and yet its growth is not entirely explained.  

I wonder what the other princesses are up to, since their own stories have not been expounded on. When compared with the character growth of discord, the two princesses have hardly changed at all in recent seasons, with Luna's only developments being in S5E13, S2E4 and very small bit in S4E19. Celestia has not had any noticeable development since season 2. Since they were created as supporting characters and not forces of nature it is a little jarring when Discord can change but these princesses do not. There is a rich bit of story that can be created using these characters, without unveiling their histories, but it has not been utilized. Knowing that these individuals are people, for lack of a better word, would make an interesting episode as it is difficult to create empathy without such an episode, as empathy is a difficult lesson to teach.

To rotate the previous idea to some degree, where does Twilight and her friends fit into pony society, are they elites, royalty, or something else? Twilight clearly does not command the respect or decorum that Luna or even Cadance does even if she is comparable to Cadance in status. Perhaps she has to earn it? If she has to earn it then how can she earn it? It would be a neat development to see ponies recognize Twilight in later episodes and respect her and her friends due to previous episodes, leading to touching moments, and an underlying network of friendship, a friend of a friend might need Twilight's help. The map directly prevents this, serving to expedite the process, but keeps the relationships shallow. A clever episode would be a group of ponies pulling out all the stops and decorum for Twilight, how does she respond? How should she respond? Should she respect the wishes of others to engage in elaborate ritual? Or should she attempt to equalize her status with that of others? What is her duty to other ponies? What are the duties of other ponies to her? 

If Twilight is a princess why does she not possess the wisdom of other princesses? Is there a way for her to pursue this wisdom, or perhaps learn that not every princess is entirely sure of her own path? The idea was hinted at during Twilight's Kingdom but never addressed. The same idea would also give character to the princesses who have been primarily, forces of plot, whose desires and goals are unknowable. There is likely more to Celestia than her desire for good, hinted by her reaction to seeing Luna again at the very beginning of the show. Luna has had a fair bit more definition in that respect, but like Celestia, her own goals, outside of realm preservation, are unknown. As Twilight and her friends approach equality and familiarity with these individuals, perhaps their stories will appear. 

All these pieces interact with each other. Twilight holding the idiot ball prevents her from hunting for the wisdom and recognition that would make her a princess in its entirety rather than a princess in just name. A lack of deep characterization and development of the other princesses keeps them separate and aloof from Twilight, even if some of them, such as Cadance, should be far more conversationally accessible than others. The map hinders the "friendship network" which likely is the closest thing  to a true kingdom twilight has, with her responsibilities to her friends and strangers, and their responsibilities to her, creating a psudo-fudal system, with her spreading of friendship being exchanged for good will. Since Twilight cannot build her own kingdom due to the map, as the map isolates instances of friendship problems rather than using an ever growing network of supporting characters to estabilsh her kingdom in the hearts of others rather than in land, and cannot pursue the wisdom of princesses, due to their inaccessibility, her character development is slowed immensely, which contributes to her growth of raw magic power, to keep her character relevant to the story, resulting in an unbalanced and potentially dangerous cycle, where she either dominates the solution with her magic, or is entirely useless due to her lack of character development. Either her magic has to be addressed, or her characterization has to be addressed, with the other members brought up to speed in effective plot power, in order to maintain balance amongst the main party (the status quo of the entire series) or else the party could become unbalanced which could alter the series immensely. 

Equestria is a great fantasy world for creation and development, perhaps as deep as Pokemon or even the Land of Oz. There are great topics and ideas to be examined here, in an environment where they can be looked at carefully. It is dangerous however, not to break the environment, no matter how strong Pikachu is, he will never be able to level mountains and defeat all challenges, and no matter how powerful Elphaba is she cannot entirely invert society. What will happen when Twilight can command great magic and level mountains? What problems will she face, that command her attention? This is the inherent problem to the show and most shows in general. What is left when your character can take on all foes? The answer is to search within Twilight, and within her friends, their fears and doubts become their challenges, that allow them to self-affirm their place in the world. Their friendship is the glue that supports them, and ultimately can hold the series together into future seasons. Whether or not it survives is up to the writers and executives that govern them, but the potential is there, the question is whether or not the show will be allowed to meet it.

A fire always burns bright, and burns hot, but the question is always, how long will it burn, until it burns out?