Quick answer to the OP's question. If I felt the need to replace brake pads in the field, I wouldn't. I'd call for a lift.

The only way I could see being concerned about this is if you do bike packing. And even then is seems unlikely. But if I were that concerned, I'd have higher end calipers that used the screw type with the small safety clip (like the GRX caliper shown above). And likely if you were doing big-time cross country touring, you would have a needle nose pliers as part of your tool kit.

For anything other than solo long distance, multi-day riding, I can't see why you would be concerned about brake pads.

Can problems occur? Sure, I've inadvertently contaminated brake pads doing maintenance and been well into the next ride before the problem surfaced. But you can complete a ride on one brake in most cases. I'm a belt and suspenders type, but I've never even thought about taking spare brake pads on a ride.

Bottom line. Anything can fail on the bike. Some are simply so rare that it makes no sense to prepare for it. Also, maintaining the bike is a good way to avoid most failures while riding.