Building on the Legendary Units post, I thought "Why not use the same technique to add a hero to a game that had players crying for heroes. The advantage is that it would allow for a hero, but within the current rules framework.
If a hero is present in a battle, then the player recieves one less comand action. This is to address the imbalance created by the presence of the hero. A hero does not exist independent of the unit she/he is fighting with. In the movement/Command face a hero may forfeit his ability for that turn and move to any other unit in that player's faction.
A hero has the ability of any one card from the faction's deck. Assign the card to the hero and remove a copy of that card from the deck for reference and to remove it as a possible draw from the command deck. Once per turn, when appropriate, the hero may "play" the card. Unlike a Legendary Unit, a hero's card may effect multiple units if that is what the card effect states.
Any time a unit that the hero is with fails a courage check or is eliminated, the opponent rolls a die, on a one the hero is removed from the game. After the battle, the hero's player rolls a die, on a six the hero is dead, otherwise he may return on any following battle.
A hero improvement is built at a cost of 2 points. Only one hero per faction may be in play at any one time.
A player with the Tavern improvement may elect to select a "Mercenary Hero" rather then follow the regular tavern rules that turn. A mercenary hero selects its card from the mercenary deck. The advantage is that the player's regular deck is not then depleted.
As an alternative, the Mercenary Hero may select a faction specific card (21-30) from any faction. This would give a player an opportunity to try some different abilities out with your faction. If you choose a card from your opponents faction it in no way limits his deck. You need to supply your own card
A chit of some sort needs to be created to represent the hero. A player can give the hero a name and backstory to add color.
A Hero can associate with a Legendary Unit and in this case the benefits do stack (add together).