I thought about replacing my Camelback with a small backpack that I can carry a bit more in. Nothing too heavy. Has anyone else tried this?

Have you tried bumping up a size in the Camelback family? I have a Rocket and H.A.W.G. (which esentially a backpack with a large bladder.) Each serve its purpose depending on which bike I'm riding and what I need to carry or not carry.

Personally I wouldn't want to travel with Yet More Stuff, let alone more stuff on my back. This will add fatigue to your shoulders and neck.

How about adding a handlebar bag instead?