First off, high five for taking the first steps towards achieving your goal. Secondly, and to answer your question, heck no, your career plan is not ludicrous! That's not to say it won't be challenging, but that's a true statement for anyone pursuing a degree in engineering (or any technical science), no matter your background or starting point. Everyone has to begin somewhere!
One of my favorite life stories is of a guy from southern California who didn't particularly like math or science, so he went to college to study music. He dropped out shortly after starting college, started a band, and really wasn't succeeding with his band or any side jobs. Then one night, driving in between gigs, he looked up and a constellation caught his eye. After some time, he noticed it had moved and he was curious as to why. He saved up some money and enrolled in an astronomy class at a local community college to learn more about the stars. That sparked more curiosity. However, he needed some prerequisite classes to continue, so he enrolled in those classes and continued bouncing around from class to class until that led him to full-time student status and attending a local university...and eventually, achieved a degree in mechanical engineering. And then he achieved another degree. And another. This guy had a late start and is famously known as the development manager and phase lead for JPL's Mars Curiosity rover's Entry, Descent, and Landing (EDL) engineering feat...the "Sky Crane." His name is Adam Steltzner, rather, Dr. Steltzner. It's a pretty inspirational story!
Back to your question, you can still work with aerospace and defense outside of SA. The best place to start is through academia in research and development and then internship/co-op. Better yet, apply to a foreign country's university and enroll as an international student. From there, pursue every internship or research opportunity available to you. I can't encourage being an international student and immersing yourself in research/intern opportunities enough! Start looking for universities that have research opportunities in propulsion, aircraft structures, sounding rockets, and general aerospace (in SA and internationally). This will give you a better idea of where you can go, for starters. International studies can also be supplemented through scholarship, grants, loans, etc., as I'm sure you may know already. So, work hard on achieving the grades now and these doors will open. The important thing to remember is that it's going to be hard, but don't give up! The outcome is far more rewarding!
Feel free to ask any other questions that may arise and I wish you the best of luck! :)