I absolutely love the costume.
Also.
Carol became Captain Marvel in 2012 and she had a movie in 2019, which is 7 years. Betsy became Captain Britain in 2019 and this means that there's a possibility that she could very well have a movie in 7 years at 2026.
I think they could go one of two ways. 1. It'd be a legacy movie-- have Brian be Captain Britain for the first act of the movie, then something happens and Betsy takes over. 2. They change the mythos and match it to current canon-- have them be twin Captain Britain's using the Amulet/Sword.
Our girl could very, very, very well be starring in her own movie. I think her separating from being just a sole X-Man would give her many more opportunities to be explored more in other mediums (MCU films, Disney+ Originals, Cartoons, Merchandise, Video Games). Whereas as "Psylocke" the X-Man, she would have to share the love with countless of other characters in which she may not win that contest.
Marvel/Disney could learn from the mistakes made when promoting Carol and give proper development and lead up to Betsy as Captain Britain. And Captain Britain has also been rumored to have come up in MCU discussion; plus when Peggy mentioned Agent Braddock.
I'd prefer if she was in her mid-to-late 20's, but you have to think about when this movie would be made, and how the actress would be older then. And I'd like to say this is an inspired casting: Saoirse Ronan. She has a unique enough look, very masculine, but feminine looking at the same time. She is a phenomenal actress (I already watched Little Women twice). And she also looks "fairy-like."