My cheap 29'r has bolt on wheels, 15mm nuts. I picked up a 15mm 'stubby' wrench that fits nicely in my seatbag. It's large enough to get your hand on, it's the same thickness as a standard wrench, just about 2/3 the length. You could pound on the end with a rock, or stomp on it with your foot if the nut is really tight. And you could use the 15mm on pedals as well. You could carry a 12,13,14 15 and be set for almost ANY emergency, but the weight would add up.
OR replace the pliers with a small vice-grip type tool, but they tend to be hard on nuts and bolt heads.
I don't ever think I've seen a 10mm axel bolt.