Try getting in touch with Big Sassy over at gamedev. He is/was working on a Streets of Rage style brawler game, so he could have some ideas on this (such as combos, hit detection). Judging by his posts, he's also a very helpful chap - though he probably won't know any Delphi, unfortunately.

I have a few ideas on how to do something like this, but nothing that's not readily apparent, so there's no real point in sharing them...