Even though many a pre-med tried their hands at research (and, of course, clinical volunteering), if only because med school adcoms seem to look at research experience favorably (the pre-meds I know can go to great lengths to accomplish their ultimate objective) research really is the only thing that can realistically cause pre-meds to consider a PhD in a biomedical science as a backup plan to med school.
Then again, if some MSc programs in the biomedical sciences are used by premeds in an attempt to bolster their dossiers for med school, are they funded? Do they come with a thesis? Or are they otherwise used to reinforce the dossiers of PhD hopefuls?
One last thing: why not use the MCAT (or any other test specifically designed for healthcare professions, such as the PCAT or the DAT) as an admissions test for PhD programs in biomedical sciences?
If I were the head of a department offering a PhD in a biomedical science, I would probably allow the use of such test scores on an experimental basis. That is, if tests designed for aspiring healthcare professionals truly were no better than the GRE at detecting biomedical scientific talent, then their use would be discontinued, but that wouldn't mean much then. In the event, however, that, say, the MCAT was proven to be a better predictor than the GRE is, in the context of biomedical graduate programs, then the GRE would no longer be required.