Would it then maybe be reasonable to make that area of Borneo part of the Chinese Stabilty map (Same actually with Singapore)?
That's a question better directed in Leoreth's direction, or for Ben to voice his opinion. But I'll give you my two cents.
I haven't pushed the envelope on this topic (Chinese stability map) in (a year?) but it's been discussed to death that while there
are territories that were under stable/lengthy (Xinjiang, Vietnam, etc.) Chinese control for centuries, it was best not to include them because of balance
as the AI already takes Tibet & Mongolia with some frequency now, either from war or post-collapse (the latter is more common due to AI inclination to attack indies).
There has been a significant portion of the userbase that has wanted an expanded Chinese stability map (among others) ever since vanilla RFC.
I always like showing this thread:
http://forums.civfanatics.com/showthread.php?t=313398 for a history lesson in RFC.
Interesting to see as well what some old timers like blizzrd and civ_king said in that thread as well.
In retrospect, the sentiment was more justified during Rhye's time, as China was under-represented and under-emphasized. (Power of the Myriads, anyone?)
Actually, Leoreth
shaved down the Chinese stability map,
but he gave it other toys and better stability, which I feel is a good tradeoff
and more accurately models the historiography in the region.
In short, TL;DR, no one read my ramblings,
it would be lovely but less necessary. That's my opinion.