Sirji if you are building a vehicle in this era, your engineering team should know the weight of the vehicle even before the first die is manufactured. The weight is not an outcome after a manufacturing process hope you agree. We are after all talking of producing a car not a baby.
I think when they envisaged the vehicle they attempted to create a crossover segment.
Now if you want to create a cross over segment you need to visually differ as well, one look at the aria from the outside and everyone would compare it with the Innova.
Heck they realized this too and look what they have on their website even today
Compare New Tata Aria - The Crossover Car With Toyota Innova
The marketing of the vehicle has hence become a case study in mba universities.
Ok so it ended up heavy, would you reduce weight or increase engine power ? No prizes to guess what tata did. Or may be that was easier. They are playing with too many unknowns in my view - attempting to create a new segment and also not addressing who are target buyers, confused proposition mixing up muv, suv, crossover. Instead they should have solely focused on killing Innova - if they want to repeat history I'll rather want them do what 407 did to the Japanese mini trucks , that was biblical and epic in my view. If they had done this to the Innova, heck Toyota would be selling the fortuner 4 lakh rupees cheaper today.
I haven't seen hexa in flesh so I'll rather not comment, but if it looks anything like a van - I would say tata is repeating history and not picking the right example from their own history to repeat.