Welcome to for the forum Lydster! An interesting mechanism that your son has thought of, HiG had a mini-expansion in development, that was quite similar about 18 months ago. I'm not sure if they continued developing it.
Generally on this thread, I think that fund-raising for the fight against COVID-19 is a worthy cause. I do not think that representing a pandemic that is estimated to take the lives of 350000 people in cardboard form is entirely tasteful. If I ask myself: If a loved one died, would I actually want to own and play Carcassonne with tiles that reproduce, and entirely belittles, that terrible experience? I would not.
I'd rather see something that is unrelated, or at least embodies the sense of international cooperation towards the greater-good, or hope, without having to model the untimely deaths of citizens.
My thoughts are out to those fighting and affected by COVID-19.