I think it's a great idea! I don't recommend coaching as a career, but I highly recommend it as a job!
Here's the main pieces of advice I'll give:
1) Coaching is, before all else, theater. Your first, last, and always most important task as a coach is to captivate your audience. Be big and loud and energetic and cartoonish and fun! Don't be the schoolteacher who stands at the front of the class and drones, be the schoolteacher who gets up and dances on the desk while singing about the subject!
If you're fun and engaging and passionate, your students will hang on your every word and put forth their best effort to learn everything they can from you. If you're boring, you could know literally everything there is to know, and it won't matter because the kids won't care to learn it.
I always say that part of every new coaches' homework should be to watch Jim Carrey or Robin WIlliams comedies. Part of what makes both of these comedians so much fun is that they have huge energy that takes up the entire room. You know for certain that every single person in that room is watching and listening to them, because they have this big cartoonish energy that you can't take your eyes away from.
Coaching is improv theater. Be big, b e loud, be goofy, above all be fun!
2) Be like Simone; take care of your own health, both physical and mental. Good coaching demands a lot of physical energy, but also a lot of emotional energy, and it can take a toll if you let it. While working as a coach, be sure to cultivate non-gymnastics skills, keep non-gymnastics friends, keep up with your non-gymnastics hobbies. Don't let gymnastics become the central thing that everything else in your life revolves around. Gymnastics will take over your entire being if you let it; for the sake of your own mental health, don't let it.
3) Always look two levels ahead. If you're coaching level 3s, keep a keen eye on your gym's level 5s. What do they struggle on? Is there any way you can preempt those struggles with your L3s?
4) There is a very simple formula to effectively train any and every skill you can possibly imagine: break it down into pieces that can be done more easily and more slowly in isolation, and see which pieces need fixing. Then take those pieces, and break them down into pieces, and repeat the process. Once you can't break it down any more, and have optimized all the pieces as best you can, build it back up.
Spoiler: you'll find that if you break them down enough, most skills end up being made of a lot of the same components: hollow, arch, handstand, strength, and visual cues.
5) Develop a basic understanding of Newtonian mechanics, and you'll already be more knowledgeable than a (depressingly) large percentage of coaches. If you can explain conservation of angular momentum in a way that a 7-year-old can understand, you're on your way to being a fantastic coach.
