I agree with everything you said. I'm absolutely stoked about her new role. Many of my fanfic ideas always has her in this exact role. This also gives Betsy the chance to really shine as an individual and not as an X-Man in the sidelines (i.e. Colossus, Angel, etc.). Yes, she's "led" X-Men teams before like X-Force, but she as CB really gives her the chance to interact with the greater MU.
When Rogue left the X-Men to join Uncanny Avengers, she really had her chance to shine as the focal character. I feel the same is going for Betsy. And this is still an X-Men book, technically. Captain Britain is actually a pretty major character and probably one of the UK's most popular marvel characters.
They're doing with Betsy what they did with Carol -- and look at where Carol is now. She is a multimedia property -- has her own movie and plays a large role in the MCU, has her own comic solo, cameos in a bunch of other Marvel comics, has her face all over toys and merchandise and retail, appears in video games.
Just imagine that for Betsy! She can be an X-Man and a greater MU character at the same time. If we have to lose the butterfly to get ALL of that, then I'm going to compromise. Yes, it sucks, but I don't think it'll ruin her character.
I really really hope this sticks. Just like how her change to an Asian body stuck for 30 years. This is also Hickman, so I feel like his changes will definitely be around for a while. It won't be a "let's do this, but change it back to the previous status quo in 2 years). We're in for the long haul, folks. And that makes me excited.