I'm personally studying bioinformatics. While I think the bit of labwork I did had some value I think you don't lose that much by instead learning through books & Anki.

As far of my skill in thinking about cognitive enhancement go, taking biochemistry couses had an interesting effect. The content of the knowledge it pretty usefless of cognitive engineering. On the other hand I have gokt a much better understanding about cognition by trying to get that kind of knowledge into my brain.

By contrast, biomedical engineering may require labs to be educated on biological principles, which are increasingly available but scarce for hobbyists; basic science textbooks are strongly variant in quality; and there isn't the equivalent of a Github for biology making non-school collaborative learning difficult.

That's not really true. If I wanted to build a better device for measuring lung function measuring I gained little of the relevant knowledge through lab work. The ideas I have about improving it would rather come from using the device for a long time for QS. The skills that I would need are skills about building hardware. That's probably something I could learn through internet research and become a resident at a hackerspace.

In the case where biomedical engineering is less flexible than I believed, I would essentially have a "jack of all trades" education meaning engineering firms in general would pass over me in favor of a more specialized candidate.

Firms often don't hire for specific skills. Provided you are smart and have skills a firm can hire you and teach you the domain specific skills that they need.