Thanks for the feedback, Eragon.
1. Simply having contact doesn't mean it should be included. Yes, Han China had contact with the Roman Empire (which they called "Da'Tseng", as I recall; it's been a while since I studied it so I hope I haven't just insulted a bunch of Chinese speakers), and in fact several Roman emperors actually sent gifts to the Chinese emperors. However, the distances were too great to maintain any more than this kind of contact, let alone any kind of military contact. So, being a primarily Euro-centric game, I opted to cut the map off at the edge of the Mauryan Empire.
Perhaps a more significant reason is that the map files are literally as large as they can possibly get; the game simply does not support a larger map. I could scale everything down even more than I already have, but that would mean starting over again...
Rest assured that contact with the Eastern world will be represented in the game, but through more abstract means. If you want more direct interaction, I can strongly recommend the Magna Terra mod.
2. Indian sea trade will not be directly connected to the Mediterranean because of several engine limitations. I might add some kind of trade modifier for holding key provinces in the trade route, though.
3. I have extended the map as far down through Aethiopia as I could find information for. If anything, I should add more provinces down the Western coast to represent Hanno's explorations, but that's a fairly low priority.
4. Engine limitations make this difficult, though it could be approached by giving river provinces the same trade access capability that roads have (I believe that Epigoni has this feature).
4.5. Certainly a possibility.
5. Adding wonders is possible, but much more than this is beyond the scope of the map mod. The total conversion will go into much more detail like what you're after