How rare and how difficult?
I like telling people, and not just you, that they need to understand how the Navy works. I do not say this to be mean, but don't plan on doing the "one-off" cool-sounding jobs. It's good to have a goal, but at some point you have to make tradeoffs (in your case, carrier aviation & culture vs. other things you might want to do). You also have to remember that goal may be limited to a very specific timeline in your career path only for you to be told: "sorry, your timing doesn't work." I remember being in your shoes thinking: "oh man the Navy has so many opportunities; I want to do them all," but the reality is everyone on the officer side is owned by a "community" within the Navy, that has to be willing to give you up for the vast majority of the "cool" opportunities that are not immediately on the path/billeted for that community. Also, each job is specifically for a specific rank and timeline +/-. Additionally, once you get off one path, it can be very difficult to get back on it; I say this because I remember thinking as a brand new Midshipman something along the lines of: "oh man, I'll fly one tour, go instruct, then do some random other cool super tactical thing, at this point I'll be old enough to want to settle down a bit, go to grad school, I'll be schooled up, go back to flying, then become an attache, then go back to flying again... yadda yadda yadda" but it's not exactly like that. There's a set path, with limited options, and while there are some off ramps, they are often permanent off-ramps, and most of those are highly selective and timing dependent, plus your community has to be willing to give you up.
