I wouldn't adjust any of the rules since they are mystically good. Deeply hidden behind the cards and dice rest all well thought out gamesystem.
But maybe it would be possible without changing to much.
The Imperial Lords, from the same expansion, had also special rules:
5 Combat dice, but only 1 hitpoint.
So, maybe in this manner: Just changing combat dice and hitpoints.
But as you said the game is good as it is.
Btw:It would have been interesting to see how an Advanced Battle Masters had turned out. It's the only Baker-GW production that hasn't an "advance treatment". Like Space Crusade or Heroquest.