My personal view: I believe there is a distinction when offering classes between SD (self defense) and MA (martial arts); words often used interchangeably, and they should not be. When teaching a SD there is no stamp. Meaning, SD is without limitations. SD is free-form, and depends on a creative process seeking to problem solve with a select array of tools. A core requirement then is variations, flexibility and adaption. A SD class encompasses and embraces any and all resources at hand to achieve the end goal quickly, over a short period of time. As a SD class is specifically and narrowly designed to target the ability to inflict seriously injury in order to disable an attack with as little engagement, engery and time as possible. Whereas, MA class is dependent on fixed and established forms and process that don't vary in structure or teaching approach. MA has prescribed techniques that are structured to be taught in a formal manner. By doing so MA is purposely confining itself to its own established protocols, tenets etc. Most MA, are defensive in nature with engagement caveats, and competition rules of engagement. The goal in a MA class unlike SD isn't anything goes, it is primarily to learn and practice the established art. That is like learning any other artisan's approach to their art. Learning MA is also to keep the art alive, to continue to exist as established. MA, hence the word "art" can be utilized as self defense, but primary experience is to function as an art. Lastly, a MA can take many years of learning and practice before reaching a level of being able to use it in a self defense. MA is an art, a specific art form. SD isn't. That is my view.
The first step is to determine your goal? What is your mission? With in that process you determine the reason and purpose for teaching others. Once that all that is established your next step is to look at yourself, what are your qualifications to teach others, as not every, despite the grandiose martial arts myth, not everyone should or can teach; regardless of how easy is seems. Once that is achieved, it is determined if you do have the personality and gift for teaching This is achieved through honest introspective and evaluation, researching the subject of teaching and what it take to be a good teacher of any sort, and by the recommendation and opinions of others. Next step is to determine what approach to teaching you will take and develop a philosophy and methodology around that? Then you decided what best suits your profile to teach, a MA or SD? Anyone can throw on a black belt and say they are a teacher. Do to the efforts of McDojo's to proliferate their profits getting a black belt means you are qualified to go out open up a school and teach. Teaching is in itself has many requirements and qualifications. Just because you have experience in an art, doesn't mean you are automatically can teach. Teaching in itself is an art, and it takes time to learn, and experience to be good at it. No one wants a incompetent instructor, or poor instruction. Being mindful and understanding what it takes to master the art of teaching doesn't fit in a gym bag with your belt. My POV is many martial artists under don't realize that teaching has requirements and qualifications, if you want to be a good teacher.
The options than become MA, SD or other. Yes, other. You can make up your own system combining techniques from various arts. You will often catch hell in the MA world for doing so. Unless, it is done in a specific manner with a specific approach and attitude. Where as SD that doesn't matter, because the more you know, the more expertise and experience in real fighting you have, the better the SD class will be. No one cares if you combined various MA techniques into one system of SD. All anyone cares in the SD world is that what you and your teaching is effective, that it is sound, and effective. In turn, it will make them effective in protecting themselves when needed. The last, is MA. Choosing to teach one specific art is a matter of the art's protocol, your skill and preference.
IMHO, teaching an art takes a tremendous commitment from a person, in time, effort, responsibility, etc. it is no walk in the park. Neither should be deciding what to teach. It is hard to be a good teacher, it is easy to be a bad one. And we aren't talking about teaching a class on organizing your closet space. Good luck, I hope my advise was helpful.