first of all thanks for taking the time to give us input.
There is one phrase here that I am not sure how to interpret:
> I'm not entirely sure how I'd go about designing a website in gimp
> to deal with this problem
The "designing a website in gimp" sounds scary to me because I then
immediately think of the overall layout and how it fluidly resizes.
I can only hope that for you it actually means producing the actual
images that go into a website.
Overall, I see that you call for support in GIMP to evaluate how
a certain image will work over a solid background color (hmmm, that
be also over a background image), and support for flexible masking to
evaluate how things work under resizing.
principal user interaction architect
man + machine interface works
http://mmiworks.net/blog : on interaction architecture
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