Hi Saim,
That is ambitious!
For Polynesians you may want something like the carrack that can transport units across oceans early, perhaps even at galley level. Alternatively you could have a lighthouse that extends a large 'no sink' region around a city. Not sure how you'd mod it though.
The Carrack is the Portuguese UU though, isn't it? I don't know why - the rest of Europe had carracks. That's a good idea for the Polynesian UU - that would really be what they're known for.
Venetians were famous for trading and had trading concessions all over the place. UB would have to be something like an improved bank, or marketplace. Ideally you want them to be able to found Civ Jewelers Corp in the middle ages and then spawn it to all its opponent in caravels. The Sumerians get an early courthouse so it may be possible. It could be a game breaker though. UU could be something like the dutch EIM.
Indonesians and Javanese may need something like more food out of their BF cross. I think they get one extra rice harvest per year in Java. How about a granary (Terrace/padi) that adds slightly more food. Or saves 60% instead of 50% of your grain.
What exactly is a BF cross, and what is a "padi"?
How would an improved workboat operate? does it yield more food or commerce from a resource square?
That's what I was thinking.
EDIT:
Here's a sort of redo the list of Indian civs, with culture rather than dynasty in mind:
India
Telugus (Satavahanas, Pallavas, etc.)
Kannadigas (Hoysalas, Mysore, Chalukyas, Rashtrakutas, Chalukyas, etc.)
Magadhis (Guptas, Mauryas, Sungas, Nandas, etc.)
Kushans (a dynasty, but they where a foreign Indianized one associated with no ethnic groups - they where however based in Gandhara)
Tamils (Cholas, Cheras, Pandyans, etc.)
Marathas
Mughals (another foreign Indianized dynasty)
Sinhalese
Delhi Sultanate
Ahom (a Tai kingdom established in Northeast India, modern Assam and the Assamese language, which is now Indo-Aryan, is named after Ahom)
Vijayanagara (either Telugu or Kannadiga, unknown)
Sikhs
Deccan sultanates
Licchavis
Or should each dynasty/state within the culture have its own civ? And where the Guptas, Mauryas, etc. even dynasties of Magadha?