Whereas it's admirable that you have so much integrity with regard to training people thoroughly, I must say there was an instructor in my OW class who was rather off-putting with just this attitude of, "I don't know if you're qualified to be certified yet." Whereas the problem was his lack of skill as an instructor.
I think you could achieve your goals of training people well by simply training anyone who meets the qualification of the agency under which you're training, no matter what their long-term goals, but teach them all the extra non-required skills you like, testing them in those skills as you please. But if anyone doesn't seem to have learned adequately to be certified, consider whether it was due to their laziness/inattentiveness or not, and if not, give them whatever extra instruction they need to get them up to snuff, and certify them.
By the way, what is this book of yours that everybody recommends, and where can I get it? Thanks.