I honestly don't think there should be many more provinces additions (maybe just european russia, Japan and interior of Arabia), the game after a few years become very slow, and Indochina and South Africa weren't really known in those times. I also don't think there should be a sea connection between China and India, I doubt there was at that time, since the main route was the silk road, but I might be wrong...
I want to add Indochina too, it's a cool place to let India and China colonize. I don't think the game will slow down that much with the remaining provinces, see the slowdown with the zilions of provinces added until now, I don't think add more 50 or so will slow down the game that much.
East Africa was just a suggestion, it's not on the "to do" list. I forgot the Kuninda Kingdom, so we'll at least 1 more province in the Himalayas
I have to investigate the chinese-indian sea connection.
So the provinces I really want to add and currently are TI are: Japan, Indochina, Sarmatia Europaea (above Rhoxolani).
The regions I want to improve with more provinces are: Greece, Sicily and maybe China, to include the minor Warring States. I have to think in Nubia and Aethiopia, maybe I'll split the provinces. I have to think the same in Arabia.
The regions I think I will add are: Inner Arabia.
I'm not sure about more provinces in the Himalaya (however I will add Kuninda). I think they were as strange to the chinese/indians as Germania to the Romans, so I have not decided yet if I make the Himalaya colonisable (with events to slow down it, maybe).
I think after balancing out a bit the priorities should be to add some decisions and missions to steer a few nations more historically, and add a few new trade goods (like silk, chinese ware, precious stones, gold, silver). A lot are already in the RIMP mode, we could just copy from them (with permission of course)...
But without the new regions we may not know how they will work out (e.g. Maurya rushing to colonise the Himalaya). New trade goods seem fine, I have to study how RIMP did that.
What do you think of these suggestions?