Rustom 2 is a dead end design
It is extremely overweight and cannot be rescued by using more powerful Piston engines
More powerful Piston engines will lead to even higher weight gain
As per DRDO report the maximum time rustim 2 t as flown is 85 minutes which means that very limited fuel is being put in the aircraft to compensate for very high weight
I hated Rustom 2's design ever since it's model was displayed 6-8 years ago!!
Despite it's inefficiency and bulkiness it'll still lumber along with some functionality!
New engines will add disproportionately more thrust than the weight addition. So, it's not a bad idea.
The fact that it'll be a 3 tonne beast with only 350kgs as payload (including EO, SAR, EW etc) makes it a laughable - it's like a driving a large truck for your weekend groceries!
The only way to rescue Rustom 2 in short term is to put in turboprop engines in conventional layout but long term solution is to adopt Saras type layout as also adopted by Euro MALE drone.
Turboprop engines might deliver more power but is deemed to guzzle more fuel. Piston engine choice was made due to its fuel efficiency.
Long term solution is to have a SINGLE REAR engine, turboprop or turbofan(like all successful UAVs in the world)
The fuselage would be practically the same design but the Twin engines will be mounted towards the back end while the wings would be pushed forward a little to compensate for the centre of gravity
Wings should be pushed BACKWARDS to compensate!
As I have repeatedly point out that even if Rustom 2 Drone ad been fully successful that is to say was built as per specifications even then it would have been useless in Himalayas which is our primary area of concern
Piston engines do not work well even with turbochargers or superchargers at high altitude in all practical situations except for experimental aircrafts
The design altitude ceiling is 30,000 ft. If they achieve that, it'll still be useful in the mountainous territory.