It seems like the barriers to innovation are insurmountable to everyone with the will to try

Why?

When it comes to running studies, you could run a study for the effect of taking Vitamin D in the morning vs. in the evening. Various QS people have found an effect for themselves. The effect should be there. As far as I know there no study establishing the effect. Doesn't seem to be difficult for someone without resources but with a decent amount of time on their hand.

As far as diagnostic tools go, we today have a lot of smart scales and blood pressure measurement devices. As far as I know nobody produced a similarly smart peak flow meter (/ FEV1). Such a device would allow the gathering of more data for a lot of people. More and better data means more opportunities for scientific insight.

On a more theoretical level I think there could be advances in organizing the large pile of biological and medical knowledge we have. I don't think that textbooks and journal articles are good mediums for transferring knowledge between scientists. Protein databases like uniprot contain a lot of information in a way that's easy to query. I think that finding ways to organize less structured biological insights and the evidence for them is an area with a high potential impact.