Although I agree with you i am still leaning towards building new capital city.
Yes we definitely need new alutsista and stuff, and Kalimantan would be easier to invade, currently most of our military power is concentrated in Java and also population in Java is huge (huge potential of militia to support the military), while in kalimantan is still quite sparse, if in java any invaders even if they succed to land they will be always under constant threat of our military or militia, there are people and settlement all over Java, and in Kalimantan there are still many place that can be used by invaders to hold their ground and strengthen them self.
Short term solution is pergeseran kekuatan, long term would be bigger defense budget = more shopping = more alutsista.