Basically it's for a deterrent efect . That's why while asking for a token of F 35 the main goal is another F 16 . whatever series that is . What are we looking for today is number . Either 2 sq of F 16V or lump sum of boneyard relic we could modify later on we go for a broke in this visit . And the assorted support of A&EW to complement the upcoming squadron.... Hell , some also say the navy itching for the poisedon to keep their fleet a float somehow in the SCS . V 22 and chinook was for army flyboys ...
Even that's the reason, a handful of F-35 would not only be very costly to purchase as Indonesia has to buy a totally new package of logistics support, software update and other stuffs that are only good for F-35A. Would an "deterrent effect" justify such spending?
Also the costs of maintanance and others may not be cost-effective for Indonesia as well. It seems Indonesia is far better off if they could spend all their money on buying more F-16V. However, that's just my opinion.