Hi Virginia,
Making such plots yourself should not be too much work.
I fully embrace the idea that data visualization and plotting are important. But this is not a plotting library, and I am reluctant to do much with the ModelResult plotting routines. I would be inclined to remove these methods completely, but I know lots of people use them. So I would say that I think these routines are okay to keep, but they are never going to be full-featured or do what everyone wants.
OTOH, if someone wanted to support a project for plotting results from lmfit, that would be fine with me. A general-purpose fitting GUI or rich set of Jupyter tools would be nice to have. I have some GUI parts for lmfit-based fitting in some of my other codes, but not quite general-purpose, say like fityk. I think that would be nice to have too, but would also be some effort.
I might ask you and others here how valuable that would be.