You always need to make your choices in life a "parallel plan" in mind. A parallel plan is an alternative plan that can lead to good places, including possible reapp or even pivot to another field. For a gap year(s), you need to choose something that you will enjoy, and makes sense in your life - including financially.
Adcoms are not singularly focused. They're able to be impressed by a host of gap year activities - if the applicant is very engaged in the activity and the activity makes sense to the story. In addition to research, successful applicants have worked as teachers, EMTs, patient navigators, as well as in business/tech jobs, or even started an NGO. Journalists, ballerinas and pro athletes have also been successful. In the gig economy, even uber-driving, nanny and elderly care can be pieced together w/ other passions, as long as balanced with continued clin exposure, comm svc. Even research-heavy institutions seek a variety of students; excellence is sought more than a carbon-copy application.
A Masters' degree is often expensive, and rarely wows an adcom. If UG academic record is blemished, MA/MS in rigorous program might sway some adcoms (but not if MCAT low, as noted). One student was an Ivy bioengineering undergrad with a 3.6 GPA, very good EC's, MCAT fine, (but pre-med office would not support as a senior). He then did a 5th year Masters in Bioengineering at his UG, getting a 4.0, and then did another research gap year while applying to MD programs. He got 3 II, with 2 acceptances. But had he not been accepted, he was on track to do any number of things with his MS bioengineering, which was his academic passion. He both strengthened the weakness in his app AND got additional training in his field of interest, (which set him up for a parallel plan if not accepted).
