I do wonder how they'll handle the logistics of such a diverse fighter fleet. They already operate F-16s, Su-27s, Su-30s, and T-50is, with Rafales also entering service. Adding J-10CEs means yet another aircraft type with its own training, maintenance, spare parts, weapons & support requirements.
That said, it certainly isn't unprecedented. Pakistan, for example, has successfully operated a mixed fighter fleet consisting of J-10CEs, JF-17s, F-16s, Mirages & F-7PGs. It will be interesting to see how Indonesia structures its force & sustainment model to manage a similarly diverse inventory while maintaining readiness & controlling costs.