We bought a brand new Avanza Velox in Jakarta about 1 year ago when we lived in Jakarta.
Last August we re-located to Bali and had the car driven by a professional to Bali for Rp5 Juta. Meanwhile, the plates were OK but, as we have changed our Kitas to Bali, we changed the plates from B to DK, when the STNK needed renewing.
It is an administration issue as it has to be removed from the Jakarta registry and included in Bali. Given patience and the right people, we have managed, and proved it is do-able.
IMO, just to get a cheaper car by this method is hardly worth the effort or costs involved.......but it can be a financial benefit as a DIY project.