I don't know what Gradient looks like, but in any case, you can't have parts of a Hatch pattern in different line weights than other parts.  I think your only option would be to define something with multiple lines very closely spaced to simulate a single heavier line, possibly three for some, two for others, getting down to singles for the lightest ones.  The spacing of them in the pattern definition would be affected by the lineweight with which you would plot it, and the scale at which you would use it.