For your information and consideration I attach the EASA recommendations (not compulsory) regarding COVID 19 measures for flights.
They are not specifically written for ballooning, but you can distil from these what you think is needed.
We have proposed to restart commercial ballooning based on these suggestions in the Netherlands. We will know next week if they have the guts to say yes to our suggestions. All the research points toward a extremely remote chance to get infected in the open air if normal hygienic measures are observed. Covering mouth and nose with protective hospital quality covers offers very limited protection if you are not trained appropriately.