An Aztec Tetrarchy

The 'Aztec Empire' was, in reality, an alliance of the city states of Tenochtitlan, Texcoco and Tlacopan, each of whose rulers had the title huetlatoani, meaning 'Eldar Speaker', often translated as Emperor. In the late-15th century, Tenochtitlan had become the pre-eminant player and its huetlatoani took the title huehuetlatoani, meaning 'Eldest Speaker' despite this, he was still theoretically primum inter pares.

My question is what it, either during the early days of the Triple Alliance or perhaps in its dying days, a more formal system of power allocation is created, with one 'Senior Emperor' and several 'Junior Emperors' and a system of apportioned spheres of decision-making (maybe by territory like Rome or by area of policy like the Athenian Archons).

Would this make the Triple Alliance more stable?

Hell, if it was better run could it actually survive a bit longer, in one form or another?
 
The problem is, the *Tetrarchy* still won't incorporate the various vassal states like Tlaxcala, which can be raided for sacrifices and tribute. That entire system - keeping weaker enemy nations alive for sport - is very dangerous. Certainly it's what gave Cortez the numbers to conquer the Empire. Even if you're butterflying European discovery for a few generations, they're a natural fifth column if any local enemy like the Tarascans gets powerful enough.
 
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