Just catching up on some of the above:
Remember, jungle is also -1h, so if you're modding the orcs tile yields, bear that in mind.
Blitz: sounds nice, but I agree it'd be overpowered. How about (and this supercedes my earlier Forced March suggestion) the March promotion is changed to require either Combat III or Orcish + Combat I. This would also simulate forced march in its way, not from extra movement but from less need to stop and rest. Additionally, if barbarians could be "taught" the value of March, you'd find less crippled units easy for the taking (yes, I'm looking at you Orthus).
Brawl: Not sure how this would be implemented, and you'd be completely hacked off if you just killed your own prized unit (hero etc), but I like the idea. What may work better would be having different tribes, and there's a chance of attcking friendly units of a different tribe. The tribes could be represented as a promotion (e.g. new units randomly get a promotion from a list of half a dozen possible tribes). At least this way, the player could try to keep the tribes seperate and minimise trouble. Hmm, mind you, am I just introducing some needless micromanagement? Perhaps it would be easier and less intrusive to implement as events, such as:
EVENT: STREET FIGHTIN' ORC
A messenger from [Braduk the Burning] reports a dispute between rival tribes has turned from a drunken brawl into a city wide riot. How should these troublemakers be dealt with?
1. Orcs will be orcs (do nothing).
1 turn of unrest, all units suffer collateral damage
+1 unhappy for 10 turns (normal speed)
2. Pay the strongest of them to beat the weaklings into line (costs level of highest xp unit x 5 gold).
All units except highest xp unit suffer collateral damage. Highest xp unit has chance to gain 1xp per other unit.
3. We need something to keep them occupied. Organise a prize fight (costs sum of levels of units x 5 gold).
Not sure how to implement, but wouldn't want to kill any units, though could leave some on 1 hp. Winning unit gains xp, and maybe possibility to gain Hero promotion.
+1 happy for 10 turns (normal speed)