This is a great idea, and I've just released an update with this feature. You should see the results in the tooltips of any solar panel: you might notice they're at 95% (with a little pollution on Nauvis), or sometimes Factorio represents it like -40% (with a lot of pollution on Nauvis).
I checked out that mod first. With some research, it seems this has been a desirable feature for a very long time, but many users/modders didn't really know how to achieve the result. That mod took an approach that was a common suggestion on related topics: clone each solar panel to make variants that produce less power, and swap the entities to the closest related variant depending on the pollution. That's quite clunky, and introduces many potential incompatibilities and problems.
I have a pretty novel approach with nearly none of the same issues. Although every aspect I can think of is better with my solution, I'll admit to one fairly large downside: mods that introduce many new types of solar panels with significantly different power outputs will probably produce results that feel imbalanced. That's because the modding API does not expose the power output of solar panels: they all appear as effectively the same thing. That's likely why the other approaches were taken: to support modded panels. My approach takes Quality into account, and I'd rather support that than introduce user-facing issues to support panels from other mods.
