I find that what little Bahasa Indonesia I know (I managed to puzzle out most of the bits from your fics! Go me!) goes a lot further in Malaysia than it does in Indonesia, especially outside the cities where my understanding of what people are saying to me drops from about 50% to maybe 10%. Because there's all those variations of the regional languages, too! I don't know much about Sundanese, but I remember being amazed by Javanese and how there's all different levels of formality in that that are separate again from Indonesian. I'm in awe of the ability to mix and match it all, really.

In conclusion: please write Muslim Indonesian Jimmy.