there is a hint of it when you declare a WAAAGH! but, yeah, otherwise they do as they are told.
I think GW is reluctant to let "traditional" animosity go, but the pre-game animosity sounds awesome.
before deployment roll d6 for each unit, 1 is a failure
1) Drunk. Unit is coming off a fungus beer bender. WS is -1 and unit cannot march for first turn while they clear their head. May charge as normal.
2) Very Drunk. Unit found some odd "edibles" in the night goblin camp. D6 members of the unit never show up for the battle. -1 to WS and no marching for 2 turns. unit may charge as normal, but must subtract 1 from WAAAGH! rolls.
3) Brawl. unit gets into some sort of pre-battle scrap. d6 st3 wounds, armor saves as normal.
4) Found a new path. Unit tries a new tactic that could help them outflank the enemy. do not deploy the unit as normal. on turn 3, roll a d6. on a 5+ the unit shows up on a random table edge (including their own) unit may move and charge as normal. on turn 4, they arrive on a 4+, turn 5, 3+, turn 6, 2+. if the unit never shows, they count as dead for victory purposes.
i need 2 more, brain not work this morning.