Level Substitution Reworked for the barbarian
I decided to go a little farther and make the barbarian level substitution separate from the fighters, to allow for rage, and to take away some of the less subtle disciplines from the barbarian. The recovery of maneuvers is different for the two classes as well.
I made rage delayed a level so that a 1st level barbarian using these options isn't too good. I also made it more difficult for barbarians to recover their maneuvers, unless they used rage to do so.
You could substitute Whirlwind Frenzy for rage, if that appeals to you.
Note that I see these as more like my versions of the warblade class, rather than "Hey here is another way to build a fighter or barbarian." To me these are the way warblades should have been done.
Fighters as Martial Adepts
Fighters can choose to devote some of their martial training to learning disciplines of the Sublime Way.
Level: 1st.
Replaces: If you select this class feature, you do not start with heavy armor or tower shield proficiency, and you do not gain a bonus feat at 1st, 4th, 8th, 12th, 16th, and 20th levels.
Benefit: You begin the game with knowledge of 3 maneuvers and 1 stance chosen from the Diamond Mind, Iron Heart, Stone Dragon, Tiger Claw, and White Raven disciplines.
Once you know a maneuver, you must ready it before you can use it. A maneuver usable by fighters is considered an extraordinary ability unless otherwise noted in its description. Your maneuvers are not affected by spell resistance, and you do not provoke attacks of opportunity when you initiate one.
You learn additional maneuvers and stances and may learn a new maneuver in place of an existing one as as a warblade of the same level.
You may recover all expended maneuvers with a standard action to attack or to do nothing more than a harmless flourish with your weapon.
At 20th level, you gain the ability to use two stances at the same time.
You may use any maneuvers, stances, feats, or items as a warblade of the same level.
You gain (4 + Int modifier) X 4 skills at 1st level, and 4 skill points + Int modifier at each addtional level.
Add the Balance, Concentration, Diplomacy, Martial Lore, and Tumble skills to your list of class skills.
Barbarians as Martial Adepts
Barbarians can use the more ferocious disciplines of the Sublime Way, and even use their rage to refocus their powers.
Level: 1st.
Replaces: If you select this class feature, you do not gain fast movement or damage reduction. Your ability to rage is diminished. All of your rage class abilities are gained one level later, and you do not gain the abilities of tireless rage, mighty rage, and rage 6/day. For instance, you gain the ability to rage 1/day at 2nd level, rage 2/day at 5th level, and so on.
Benefit: You begin the game with knowledge of 3 maneuvers and 1 stance chosen from the Iron Heart, Stone Dragon, and Tiger Claw disciplines.
Once you know a maneuver, you must ready it before you can use it. A maneuver usable by barbarians is considered an extraordinary ability unless otherwise noted in its description. Your maneuvers are not affected by spell resistance, and you do not provoke attacks of opportunity when you initiate one.
You learn additional maneuvers and stances and may learn a new maneuver in place of an existing one as as a warblade of the same level.
You may recover a single expended maneuver with a standard action to attack or to do nothing more than a harmless flourish with your weapon. You also recover all expended maneuvers whenever you go into a rage.
At 20th level, you gain the ability to use two stances at the same time.
You may use any maneuvers, stances, feats, or items as a warblade of the same level, as long as they do not require access to the Diamond Mind or White Raven disciplines or the Concentration or Diplomacy skills.
Add the Balance, Martial Lore, and Tumble skills to your list of class skills.