've got an idea for aztec favour -
Youstart the game with an emperor (kinda like the pharoah) with a random name like montezuma (if he's died you'd get montezuma II a minute later) The pharoah can move quite fast (about 4.5) and has a reasonable LOS but for balance isues can't pick up relics. He'd be bad at fighting but would have about *10 damage modifier vs mu's and would give all friendsly units in a smallish radius *2 modifier vs mu. If he or one of the units in his radius kills a unit then you'd get favour (you'd get lots of favour if the emperor killed the unit)
You could also get priest which can pick up relics and get favour for killing and have a *4 bonus vs mu's but aren't affected by the emerors radius.
This fit's in with the aztec type flavour - your priests and your emperor get favour but most of the time your units are doing the killing - it's also less complicated than the prisoner idea.
Aztec's obviosly wouldn't have cavalry but would have strong infantry and archers. Infantry could include eagle warriors (bonus vs. cavalry and archers) and jaguar warriors (totally maul infantry even ta's)
A really cool idea for a last age gp would be effectivelly the end of the world - an earthquake and meteor shower hits everywhere on the map for about 10 seconds.
I don't know much about the aztec's but they were my favourite civ in aok (21 damage champions) and I'd love to see them in aok.
Also some more ideas for the xpack
1) protect the god n=mode - your god comes down to earth at the start with no powers or attack or anything and you have to defend him (regicide basically)
2) see chat in recorded games
3) Have dwarven warriors for the norse that cost about 60 gold and 5 favour, they would have weak pistols for long range but would turn to axes for cloase combat. (norse dwarves could be turned into these instead of ulfsarks)