Boxing normally does good tactical foot work (as it's called here sometimes). As, I understand it, so does Kempo. I'm getting this from your User CP, by the way. If you need more, a good source would be dance. Strange as it sounds, I'm serious. Perhaps you would like to here how I know this. Alright...
My Cuong Nhu Sensei is cross training in Wing Chun and he teaches some of the upper ranks the material. Before this I wasn't too good in sparring, this diffenitly helped. Once contact was made (espically on my terms), the other guy was S.O.L. But getting to the point where we were on my terms was the hard part. From my readings I ran across this tyle called Jade Ring Mantis Kung Fu. It's focus is on useing strange foot work to get their opponents into a bad place, or simply hide their intentions. There was no further discussions on the matter, and I couldn't find any other sites that mention it, so I put it in the back of my mind.
Then I ran across this factoid about Bruce Lee. Turns out he did jazz dance to improve his foot work. And he allegedly danced before his fights. I Remembered the Jade Ring concept, and put one and one together and got three. I bought 2 books on ball room danceing and tried it out. Works beautifully.
Keep in mind though, doing dance is demanding. Its a good cardio work out. And you're going to have to do some serious tweaking to get it to work well in a more martial atmosphere.
good luck and good training