Okay, here is my followup response:
1) This biggest part about traders having to spend so much time in the research/trial and error phase before they come up with a working system, if they ever do, is the time lost chasing after false leads, and having to retrace ones steps and proceed in a new direction. This part is essentially the "hamster wheel" of R&D/Trial and error until one gets a good footing, which can easily take years to get past.
The purpose of mentoring is to enable the student to skip all the time spent going down fruitless paths and concentrate their focus on understanding the mechanics and nuances of the right path.
As such, having a good mentor should result in far less time in coming up to speed and as a result far less pain.
I don't understand what you mean by your statement that each system is personal. A mentor should be able to tell their student exactly what they do, and from there the student can either seek to replicate ortailor it to their own risk preferences. A good working system can be passed on to another person doing the same type of trading- it doesn't have to be different.
3) Just to be clear, you make enough money for you and your family to live on solely by trading? You mentioned you also had other businesses, but I wanted to be sure you meant you make a living from trading rather than just making "some money" which way not be enough to provide for the needs of the household.
I'm also unclear on why you don't know what your performance is. Making a living via trading gives you your daily P/L counts. Your yearly tax forms has you submitting your P/L for the year which should spell out how you're doing pretty clearly. How do you not know your stats?
5) I agree that just presenting your methodology doesn't mean people would understand it well enough to execute it properly, but it shouldn't be an issue in showing the general summary of your method without having to dig into the weeds.
It's the same concept as showing a broad general presentation of your style (50Kft view) , a closer look view (100ft view), and the mentoring would come in dealing with the all the trees in the forest detailed view.
If you're not mentoring on a specific methodology/plan, the it sounds more like a "coaching" position rather than mentoring.