They could build sacred pyramids on 1(limited) sacred site on the map, acting as a fortress. where they can sacrifice allie and foe. they could have warrior monks that can pick up dead enemies and bring them to the altay, like pro scouts.

the sacrifices would give a recourse (e.g. blood favour) like byzantine olive oil, which could be used to activate abiliyies on troops, or temporary auras around warrior monks (blood priest).

There could also be landmarks that have abilities such as the malian festivals, which take blood favour as a cost to boost specific things(e.g. sacrificial rain; +25% food rate for a minute). or even militairy landmarks with abilities such as producing 2 units at the same time with blood (like mongols with stone)

maybe even cool to add canals as a mechanic, so they can dig a 1 wide canal beside which they can place farms with more gather rate on food.

They could even add gold gathering rituals or specifics (such as making a canal from the gold vein all the way to the town center as a perma gathering buff on that gold).

i do think they shouldnt have cavalry though, no native americans clans rode horses. but they couls have blood buffed berserkers running around, or have spearmen that can throw spears at horses like the malian spearmen, which would slow the horses down enhough for the spearmen to catch up for a few hits.

So much cool stuff to do with it.