I find it kind of ridiculous that the only way to obtain walnuts is basically to defoliate an entire tree to get at best a handful of nuts. I think it would be preferable to handle the nuts the same way fruits are handled currently, which is incidentally the way the mod "Wildcraft: Fruits and Nuts" does it.
Actually, in an ideal world, I think all trees should grow the way fruit trees do, i.e. slowly but incrementally. Of course, they should also have different size limits, depending on species.