PT DI can't handle much complex project beyond what is already in their portofolio to begin with and what they already doing is not quite right at several parameter if we are looking from business model and profit oriented market scheme they are doing
Remember that defence industry is a monopsoni.
Like what PAL hve been doing, PTDI can also expand their capacity and getting help from financial institution to boost their CAPEX and OPEX, as long as the user (ie TNI AU, the single buyer in monopsonical industry structure) commited to purchase a certain number of airframe that achieve economies of scale (which ensure PTDI’s return on investment and creditor’s approval).
How many airframe that we need to make such project to be economically viable? It needs a detail calculation, but looking into similar project in India and Brazil, at least TNI AU need to order 36-48 unit of F-21 (or Gripen) to PTDI in the time span of 4 years (12 unit per year).
This project structure can also be applied to IFX project simultaneously. Kertajati has plenty of space for these two projects. State owned banks also has plenty of liquidity to finance these projects as long as TNI AU/MoD commited for a longterm contract.
in term of ToT, we can get different key technology from the two projects (ie airframe design from IFX; system design/integration from F-21/Gripen).