Obviously, weight is a huge issue, since axes are inherently heavy.
@Outdoors_on_the_Cheap believes the best option is a light axe head with a long handle. He prefers an axe weighing 1.0-1.5 lbs, and a handle length closer to 20-24 inches.
Somebody else in the comments says they think an axe head that weighs 1.5-2.0 lbs is better. *shrug*
I've heard suggestions that you use a machete to baton, since machetes are more versatile than batoning with a knife, and machetes weigh less than an axe. [2]
There are some machetes that are both short and have a thick blade: [1][2][3][4] These are sometimes known as a bolo knife.