I think it’s difficult to improve on the handwavy argument that maybe wild animals suffer more, so we are better off if there are fewer of them. I think that people who care about small invertebrates are probably better off supporting invertebrate charities that you mentioned than funding such complex research project, which might not end up changing the behaviour of that many people (unless it changes Open Philanthropy’s grantmaking).
Persuading people to improve the lives of wild arthropods is hard, but the welfare of arthropods can also be increased by increasing/​decreasing forest area if they have positive/​negative lives, and there many interventions causing this which are more broadly appealing. For example, one could double down on nature conservation, and promote terraforming if one thought wild arthropods to have positive lives.
Thanks for the additional thoughts, Saulius!
Persuading people to improve the lives of wild arthropods is hard, but the welfare of arthropods can also be increased by increasing/​decreasing forest area if they have positive/​negative lives, and there many interventions causing this which are more broadly appealing. For example, one could double down on nature conservation, and promote terraforming if one thought wild arthropods to have positive lives.