Probably a bit too late to ask this question but I have to ask, If Twilight had never become an Alicorn where did everyone expect her character to go? What did they think her end goal would be? Where did they expect Twilight would be 10 years from now?

If i had to guess she probably wanted to follow in Starswirl the Bearded foot steps but the show never said what Twilight end goal was before she became a alicorn

Assuming that Alicorn is not a requirement for being a princess, maybe she would have become a princess anyway in some sort of retirement plan for Celestia anyway. It would make some degree of sense for her to change leadership from forever alicorn to regular ponies self governance.

University professor, teaching the Magic of Friendship (or just magic in general) at the doctorate level.

Honestly? I liked the idea that she would just become a wise old mare with a lot of knowledge of spellcraft, who helped teach other ponies the magic of friendship. I never gave her much thought. It's Silver Spoon I was always interested in.

A court mage or a professor in Celestia's School for Gifted Unicorns.

Twilicorn should have been the end result of all these years of learning and experience imo.
All the various bits and pieces come together and Twilight finally "get's it", and gets her wings. Series over. She made it!