How about make an aztec mod?!
I meen to add more provinces to amerika
To make 2 or 3 nations there
1 nation is old-style Aztecs with the same units and same stile of fight(maybe add some old-style units)
2 nation is modern Aztecs with little vanilla units and a lot of viking-like units and some more modern new units (with armor with modern weapon)
3 nation is Vikings & semi-vikings semi-natives, they are the rescued people from west village in islandia, they would have a starting little army of vikings and later viking-like native units with modern weapon
So i think it would be fun to fight in amerika and after that get to Europe by the north way with some elite New Aztecs warriors with the mails and shields and swords =)
Or for example to make a lot of scripts; When u meet some mount units u also became to construct them =) When u meet pikemens u also can sonstruct them and so on =)