Constitution of the Inca Confederation:
The Inca Confederation will be divided into Confederations, with Inca territory being the Confederation of Andea, and any tribes that join the Inca Confederation will be given their own Confederation.
Executive:
The current King of Andea will be the King of the Inca Confederation. The king is king for life. If the king does not appoint a successor, the assembly will vote on a new king. The king must approve all laws passed by the assembly.
Legislative:
Each Confederation will send 10 elected representatives to the Inca Confederation Assembly. The Assembly has the power to pass laws. If 3/4 of the assembly pass a law, the law may not be vetoed by the king.
Confederations:
Confederations may make their own laws, as long as they don't conflict with the laws of the Inca Confederation.
To Argentina:
From the Inca Condederation:
We offer you confederation status. This means you will send 10 representatives to the Inca Confederation Assembly, but be allowed to make your own laws.
(Argentina will still be NPC, but will have to abide by Inca Confederation laws, like a vassal, sort of)