I agree with some of your reasoning, but still wouldn't want to try and torque down track nuts with anything too small or flimsy. I carry a halfords 15mm spanner and use the ring end for everything.
Once solution to make tools easier to carry and find is to have a small pouch with all your tools in it. I've got a multi tool, leatherman, chainring bolt tool, puncture kit in mine and carry a 15mm spanner and pump in my bag pocket.
One thing you could do is get a cheap 13/15 cone spanner. Would handle track nuts in an emergency and will do your brake too.
I agree with some of your reasoning, but still wouldn't want to try and torque down track nuts with anything too small or flimsy. I carry a halfords 15mm spanner and use the ring end for everything.
Once solution to make tools easier to carry and find is to have a small pouch with all your tools in it. I've got a multi tool, leatherman, chainring bolt tool, puncture kit in mine and carry a 15mm spanner and pump in my bag pocket.
One thing you could do is get a cheap 13/15 cone spanner. Would handle track nuts in an emergency and will do your brake too.