The efforts by https://1daysooner.org/ to use human challenge trials to speed up vaccine development make me think about the potential of advocacy for "human challenge" type experiments in other domains where consequentialists might conclude there hasn't been enough "ethically questionable" randomized experimentation on humans. 2 examples come to mind:
My impression of the nutrition field is that it's very hard to get causal evidence because people won't change their diet at random for an experiment.
Why We Sleep has been a very influential book, but the sleep science research it draws upon is usually observational and/or relies on short time-spans. Alexey Guzey's critique and self-experiment have both cast doubt on its conclusions to some extent.
Getting 1,000 people to sign up and randomly contracting 500 of them to do X for a year, where X is something like being vegan or sleeping for 6.5 hours per day, could be valuable.
Challenge trials face resistance for very valid historical reasons - this podcast has a good summary. https://80000hours.org/podcast/episodes/marc-lipsitch-winning-or-losing-against-covid19-and-epidemiology/