I'm feeling where you're coming from here Lee Chiang Po! Nice post.
It also interests me that we are discussing times that teaching with no forms was tried and tested and failed. That the absence of forms deteriorate students progression.
This IMHO, is not so. Have a look at the Gulao (Kulo) practitioners from Fung family as an example. What they have held onto ARE the san sau (loose applications) of Leung Jan himself (if all the research lines up like I think it does). They also have a wealth of literatutre/kuen kuit that keep the theories in place (withot the need to have a form)
And so, 3 Forms must be practised? No. But to gain an overall picture of the 'style' of Wing Chun I do believe in having a knowledge of the forms. We MUST KNOW what they're for. EXACTLY. No guessing. People who have been told or shown will know what I'm saying here (I hope!)
Forms also 'change' and develop with time, they're not supposed to be so restrictive as we grow older. They do become very personal IMO.