There is no governing body in Martial Arts. You could establish your own organization that would "certify" you. I cut "instructor" certificates all the time for my guys that need to have them to teach programs at Army Base Gyms or places like the YMCA.
I do not suggest for one minute that your certs are being given to students who are not capable.Nevertheless to give such advice to others to set up their own group without some quality checks is fraught with danger. There is a danger that any Tom ,Dick or Harry could set up their own group, call themselves Tenth dan, teach rubbish and charge a fortune to unsuspecting people.Therein lies the danger. If absolutely anybody can do what you suggest imo this is a recipe for disaster.
Before long you would have what I call John Wayne aikido instructors.A bunch of cowboys,
Self promoted guys with vastly inflated ranks, titles.Heaven forbid.Cheers, Joe.