Of course there are other options, such as the use of the stepping punch as a strike, diverts the mind from other possibilites, that of the karate armbar.
To try and put this into words I'd share:
An opponent offers their left arm say to grab you before striking.
With your left arm you roll into a grab of their wrist as you shift say 20 degrees to the right and allow your right foot to slide back to a classic left front stance.
Then your left hand chambers, with the normal rotation as you hold their arm. That rolls their arm slightly over, and you start your stepping punch, not to strike them but to slide the bottom of your arm across their triceps insertion....
So you chamber as you step and punch, and in the process stick their face into the ground, with a variation of a rolling arm bar.
Works for me, and it is also a pure stepping punch, you're just not hitting anything.
If you really work on every kata variation of that movement, especially the various leading techniques, you'll find there are quite a few ways to make the same usage work against various attacks.
pleasantly,
Victor Smith
Bushi No Te Isshinryu
www.funkydragon.com/bushi