Yup I would love those too and did consider all of them for my list excepts Lines under/over.
As for diffusion curves have you tried any of the 2 free editors?
I find the concept really cool but very hard to work with, might be because they are very slow and the editors are a bit buggy.
Would be cool if someone made a quicker version of them, perhaps more like a 3d program in which you render the full quality picture.
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