critique wanted How do you write a GOOD alicorn OC?

[Shine Runner 20]

I'm writing a story about a pony's ascension to alicorn status, but I'd like to do it in a compelling way that's not going to annoy the reader/viewer.

So far, he's in a Gary Stu situation. Destined to be the first (and currently only) alicorn prince, son of Starlight and Sunburst, well-acquainted with several main characters, and is the apprentice of Luna (who has had to come out of retirement to teach him.)

He is not going to rule over Equestria, but he will instead fill Luna's role of helping ponies deal with their nightmares. Perhaps he'll have to deal with a larger threat, or he could become an alicorn simply by learning how to do his task well. I'm not sure which route will be received the best!

I was thinking on writing him as someone with depression. Maybe he doesn't want to accept his destiny as the guardian of dreams, and would instead prefer to do something else, like bake cookies or do standup comedy. Maybe he's a chronic procrastinator, or the type of character who compulsively makes everything into a joke to cope with stress. Luna is very serious about her work, and it would cause conflict if her apprentice wasn't interested in or motivated to do the tasks she deems sacred. And, as the only pony who has ever guarded dreams, I'm sure she sees herself as the absolute expert.

Alternatively, he could be overly enthusiastic about his new position, and screw things up by making all nightmares into silly, funny dreams instead of dealing with the root of the problem. Maybe he has some sort of nightmare fear of his own that he can't get rid of, and he over exerts himself trying to help others to avoid his own shadow. Once again, not sure which direction is best.

Kinda leaning towards him being a bit rebellious, too. His mother and father (and Twilight and "Aunt" Trixie) are all very much intelligent overachievers with important jobs. Maybe they hold our protagonist to strictly high standards, and his dream guardian destiny is only compounding upon his stress. He has big horseshoes to fill, and perhaps he feels intimidated and/or constricted by it all.

What tips, critiques, and general feedback do you all have? I really want to sharpen this story and have a well-developed protagonist!