And if TNI-AL really urgently needs more vessels, than more TF-100/Istanbul Class frigates can be an option.
If budget allowed it. Trump war make most of nations has to calculate budget realities again. The problem with Asagiri class more on can those become affordable to TNI-AL operational budget. I believe that after Garibaldi, any large gas turbine vessels need to be calculate again on all the potential upgrade and cost to operate.
More likely the last 4 Asagiri, which had received some modernization and are common blk. ASROCs, Mk-29 Seasparrows, Harpoons likely to be removed. Not sure about the Phalanx / Mk-15s though.
Potential I believe TNI-AL want to bargain with US on ASROC's, as I sense they are more interested to Asagiri on the ASW capabilities. Something that TNI-AL still lacking with spesialise assets on that. TNI-AL can use Euro/Turkiye SSM, CIWS and SAM rather then US ones.
Also at this moment has to be remind the availability of manning. Crews from those 5 Van Speijks potentially can only available to manned 2 Istiff and 2 Asagiri. I don't think even Japan want to transfer those 4 last Asagiri, all can be taken by TNI-AL.
Manning especially available trained crew is matter. Most of TNI-AL crews are being use with Corvettes and Patrol Vessels. Moving on to Frigate in my opinion need to be further training. Thus most likely any new Frigates will have to take crews from those 5 Van Speijks.
Maybe getting some Oyashio submarines to replace the Type 209/1300 is a better option.
That's the plan, but from what I gather the batch that Indonesia interest are the ones that already upgrade to 'close' to Soryu class standard. Those are part of later batch of Oyashio. Japan don't want to grant them, but export them at market value. The value also include potential upgrade to be 'up to' Soryu even closing in to Taiho standard. Plus reconditioning on the hull, to make it operationable for at least to 2040+. All this will be done at Japan yards, as PAL facilities will be focusing with Scorpene Evo.
So getting Oyashio even second hand will not be cheap, even if Japan provide some 'discount' on that. It still will be with Japanese standard, which we know is outstanding on their SSK, but again come with increase prices. This will not be DSME 209 standard, it can even be on par with new Scorpene Evo.