PAC has already mentioned a 200HP engine for its MALE UCAV. I am not sure its procured or indigenous.I think as drones are becoming more and more common, we should focus on building cheap and simple aero-engines, the older variants of the CH-4 use piston engines making 100 hp. Something like that can be made in the country by private vendors, such as Millat or even HIT/PAC.
Or we could use the Lycoming off of the Super Mushak, reverse engineer it and voila. (It's a very simple engine, air cooled, no complex alloys etc...)