Sorry,



Shimmer could have learned that power persuit is like you said- a naive attempt to jealously control what doesn't have to be controlled



Thus there is no "should" for such control- thus there is no destiney, and such ideas are not needed



This in turn could have opened her eyes to the same problems in celestia and all her ilk that lead to problems including shimmer's rebellion



Negligence from heroic things breeds justice from a villainous source - pretty non substantial myths help motivate the creation of self

Defeating concrete things



Shimmer could have become enlightened beyond her would be saviors by seeing her own self absorbed ignorance reflected in Equestrian status quo leaders and conscripts from their relative philosophy of dues ex machina being beyond question and predetermined just because they say and believe the integration of friendship makes it so- along with complete capitulation to the non sentient demands of the elements of harmony ... Along with the woeful attitude of "win = right"



She could have brought to alignment that friendship is never about power, though the princesses with everything to lose would obviously disagree, and the elements would just find new hosts to puppeteer, and when you say that friendship is magic- it might make power available, but that is not the Magic the phrase refers to, but rather what wonderful things it allows to happen with virtually nothing at all-



That friendship makes it possible for a dark age mideval style of life to be complete paradise in of itself honest and sincere - all the little things are a blessing- complete satisfaction



Not bullshit after the fact that events are excuses for self entitled delusion to rule everyone's heart and mind through tribal group mentality



Shimmer could be the one to see how friendship is used either intentionally or unintentionally that the virtues of friendship are a means to yoke ponies into fodder for the status quo- whether or not the status quo can repel the hazards of the Equestria world



We didn't really apriciate the show because of hierarchal power plays did we?



Shimmer could have been the voice that confirms "No, because that would be wrong."



As for the example of villainy- she could have been the villain that shows a would be princess that titles are just illusions to fool others and they are very inappropriate especially in the case of actual family like friendship



Or she could have been the villain that shows a deeper problem with Equestria- a universal danger or rot that Shows how ignorance is at play in some of the worst ways simply because ponies can't be bothered to care about it.



Or an actual villain that is a thorn in the princess delusion that makes it impossible to simply continence away or outright defeat reality



Any of theses would have been an improvement, and would add more along with the prodical repentance - how negative emotions were a volitle by product of reasonable disgust with a problem



Besides, power and titles never made a destined hero anyway .... And they won't either



Is what shimmer could have shown