I can see some of what you are thinking, but I also think you are creating problems for yourself.
I agree that it important to have a curriculum of target aims at all levels. I think yo uahve to be very careful to keep centred on individuality if you do this, though.
Yes, that is why my program is the work of pure genius

. Okay, but really, you are right, of course. However, I have been developing a bit in my philosophy. For one, just like there are general ways that our bodies move and therefore general principles to piano technic, there are also general things about music that I think everybody should know (like scales, for example). I feel that this is the case for anybody who would like to be capable of playing the piano in some way for the rest of their life. And, more than that, I have been feeling lately like I have certain things to offer and if that is not what people want, there are other teachers "out there" for those who don't want what I have. So, yes, individuality, but I aim to attract a certian "type" to my program.
Just like technique will develop in detail per each individual, though there are genearl principles applicable to almost everybody, it is the same with muscial development in general. That is actually exactly where and why they graduate to their next phase of learning.
I also agree that students should be heading towards being independent learners - able to self-criticise and make choices about practice and repertoire, etc. The teacher becomes mentor and coach rather than instructor. Still, I think an accomplished learner needs a "teacher" as much as a beginner. Yes, maybe less frequently, but again that is individual.
Yes, I am not aiming to "leave" the students and I am not sure what form this all would take (though in some ways it's already starting to take form "on its own"

). And, yes, the point of the second phase is that they would like to learn in some very specific ways and by this point they will know how to learn, so I may assign them a book to read or so and check in with them on this in our lesson.
I think the learner needs to have a large say in their decision about having a teacher at this level. However, once they have decided they need the mentor, it is up to the practicalities and the teacher's decisions and convenience must be respected. If you start seeing a student occassionally, it potentially becomes logistically difficult. Your whole schedule then hangs on keeping time available for a lesson every few weeks. I find this very frustrating.
I agree that the teacher's time and convenience must be respected, this is fundamental in how I run my business. And, that is why I would still have some very specific things laid out in how we go about these kinds of lessons. For example, if they are meeting with me for let's say, 2 lessons a month for an hour, they would trade off weeks with another person in a similar situation. I would probably reserve certain hours of each day for this type of student. All of my rules would still be intact.
Don't you find that different students have long before 3-5 years decided if they want to learn seriously/Classically or just for fun? I think you might also find this a tricky way of categorising your programme.
Actually, I am not really clear on what this means or how it would actually change my program. For one, after 3-6 months I will review their work and possibly weed people out at this point. If they don't fit with my program, we will figure this out and move on. The main thing is that after a point, they will decide if they no longer wish to have lessons, would like to switch to a different teacher for a specific reason, or would like to continue with me in a specific manner. This will not change my program in any way that it would make it trickier than it already is.